Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Tom Van Baak]

> My research group has had some good experiences using products from Endace (
> http://www.endace.com/) for network timing measurement at the ethernet
> level. I don't have a pointer immediately to the work, but if there is
> interest can ask tomorrow at work. The gist of it though was to understand

Hi Erich,

You are welcome to post your experiences with synchronization or network timing 
measurements on the list or to solicit methods to time packets to the 
microsecond or nanosecond. The rest of your agenda is straying far off-topic 
and you need to find or create a forum elsewhere. It appears you have misread 
the focus of this group.

Please re-read the intro page (leapsecond.com/time-nuts.htm) or the archives 
(www.febo.com/pipermail/time-nuts/). If you have questions contact me directly.

Thanks,
/tvb


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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Eric Garner]

I'm an applications engineer for a company that makes Ethernet controllers
and PHYs. Some of our customers use crystals (more often oscillators) that
they selected based on price rather than performance. when i'm debugging a
customer issue replacing the clock source with a synthesizer is a good
troubleshooting aid. I's also useful when trying to prove that a low
quality clock source (or clock distribution network) in a link partner is
producing a poor (usually jittery) output that makes it hard for our parts
to achieve link.



On Fri, Nov 30, 2012 at 5:06 PM, Jim Welch  wrote:

> OK, I'll bite.  Why?
>
> Jim
>
> >>>I've never done it using to the RTC crystal, but I  do it quite
> frequently in my Day Job to >>>Ethernet controllers on those same pc mother
> boards.
> >>>
> >>>-Eric
>
> On Fri, Nov 30, 2012 at 4:10 PM, Sarah White  wrote:
>
> > On 11/30/2012 6:30 PM, Eric Garner wrote:
> > > the actual RTC on modern (Intel based) PC's is driven from a
> > > standard
> > > 32,768 Hz crystal attached to the PCH. some of them are in
> > > incredibly
> > small
> > > packages now instead of the old tuning fork-in-a-can ones. peeling
> > > off
> > the
> > > load caps and crystal from the board would allow you plenty of
> > > spaces to tack down a lead from an external synthesizer.
> >
> > Yeah, the one on the (Soekis) example was pretty small. So far none of
> > of the replies have indicated that anyone on here has experience
> > beyond an embedded system.
> >
> > Mostly I started this thread because there have been a few with people
> > discussing implementing NTP on embedded microcontrollers, arduino, etc.
> > and I was thinking of doing it from the other side (turning a nice-ish
> > server into a rock-solid timekeeper)
> >
> > Thanks so far everyone. Really impressed that I already managed to get
> > 4x replies so quickly :)
> >
> >
> >
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> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > and follow the instructions there.
> >
>
>
>
> --
> --Eric
> _
> Eric Garner
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-- 
--Eric
_
Eric Garner
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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Erich Heine]

On Sun, Dec 2, 2012 at 3:16 PM, Magnus Danielson  wrote:

> Erich,
>
>
> On 12/02/2012 08:54 PM, Erich Heine wrote:
>
>> Jonathan,
>>
>> My research group has had some good experiences using products from
>> Endace (
>> http://www.endace.com/) for network timing measurement at the ethernet
>> level. I don't have a pointer immediately to the work, but if there is
>> interest can ask tomorrow at work. The gist of it though was to understand
>> precise timing characteristics of network switches for better simulation.
>> Examining the time "in switch" for various packets at the microsecond
>> level
>> was needed to understand various delay curves for different network loads,
>> with an ultimate goal of proper statistical modeling reflecting reality as
>> close as possible.
>>
>
> This is a bold challenge, it's a difficult task (clear speak: there is a
> reason for this to be a research field, industry never *really* got it
> under control).
>
>
It is a challenge. I'll have to re evaluate my understanding of the timing
characteristics of the card in light of my new and growing knowledge on
timing. However, this is what I understand now:

I'm sure the timing isn't perfect, but we mitigated some of the potential
clock issues by doing many runs of tests. Further a single endace DAG card
has 2 or 4 network ports on it, so timing can be measured across a network
to the same card with the same reference clock which helps simplify error
source.  (The card has a feature which allows time stamping packets on the
card from that reference clock). Also there is a mechanism by which the
endace cards can be connected directly to each other to synchronize their
clocks to each other, so packet timings across cards can well measured.

I wasn't very involved in the details of the project I'm describing, so I
can't speak to how well any one of those functionalities of the cards
performed, nor how much error we saw or tolerated, I'll ask those folks
later today (as I happen to have a meeting with them about other stuff
anyway :))

One thing I can speak to though, is that in simulation of the type they are
doing - the general granularity of the simulation results are on the order
of 10^-3, so understanding the switches at 10^-6 isn't used directly in the
simulation, but rather to build probability distribution functions that
capture the behavior of the switches well enough to see cumulative results
comparable to observed networking conditions (e.g. the result of N switches
handling serializing events under certain loads will get packet trains like
$X and other loads like $Y and so on). One thing the PI on that project
mentioned was the shape of those functions being correct is the highest
priority. I understand this to mean that the errors "average out" (not an
actual mean, but through some statistics I don't understand all the way yet
they stop being significant compared to other issues).

Perhaps I'll need to point those researchers at this list to find out ways
to better get the timings they want :)


>  I personally have also used endace products to measure packet timings for
>> research, but I didn't need so much precision for that work - however I
>> can
>> say they have a good API and decent tech support for interacting with
>> their
>> cards and products.
>>
>
> Is there native support with Linux kernels?
> It would be very nice to have the support using SO_TIMESTAMP and friends.
>
>
It's been a couple of years since I got deep on this, so I don't remember
details. I do know all the work we've done with the cards was on Linux, and
it worked nicely - I had no issues that were OS related. One thing about
the paradigm for the DAG cards is they are not in the standard networking
stack. They expose themselves from the kernel in a different way via an API
(which Endace provides the source for). To do IP networking with them, you
need to provided your own network stack in userland - however this is out
of the scope of the companies goal. They are really about providing high
speed layer2 access. I believe their primary use cases are research like we
did, and extremely low-latency communications between machines in clusters
(targeting high frequency traders and the like).


> Cheers,
> Magnus
>
>
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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Magnus Danielson]

Matt,

On 12/02/2012 11:51 PM, Matt Davis wrote:

Date: Sun, 02 Dec 2012 22:16:52 +0100
From: Magnus Danielson

On 12/02/2012 08:54 PM, Erich Heine wrote:

Examining the time "in switch" for various packets at the microsecond level
was needed to understand various delay curves for different network loads,
with an ultimate goal of proper statistical modeling reflecting reality as
close as possible.


This is a bold challenge, it's a difficult task (clear speak: there is a
reason for this to be a research field, industry never *really* got it
under control).


I agree with Magus, but measuring in-host (or in-switch) timing is
still possible.


Indeed. It is possible to measure, but difficult to fully model and 
characterize. A friend of me did his PhD on the fractal behaviour of 
network trafic. Then, even he didn't nailed it in a good way.



 The research team I am with presented a paper at
ISPCS this year on the measuring of in-host latencies and looking at
where packet timestamps take place, such as SO_TIMESTAMP as Magnus
mentions below.  I will point you to a link to our docs, email me off
the list if you do not have access to the IEEE online journals.  The
paper is mainly focused on BSD systems; however, BSD is not unheard of
in the switch world so maybe it can give you a few tricks for what you
want to accomplish regarding your in-switch timing.
Paper: "Probing the Latencies of Software Timestamping"
http://www.synclab.org/docs/


People should dive into that link, there is a few goodies there it seems 
from just pulling one paper.


Thanks for providing the pointer, Matt!

Cheers,
Magnus

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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Matt Davis]

> Date: Sun, 02 Dec 2012 22:16:52 +0100
> From: Magnus Danielson 
>
> On 12/02/2012 08:54 PM, Erich Heine wrote:
>> Examining the time "in switch" for various packets at the microsecond level
>> was needed to understand various delay curves for different network loads,
>> with an ultimate goal of proper statistical modeling reflecting reality as
>> close as possible.
>
> This is a bold challenge, it's a difficult task (clear speak: there is a
> reason for this to be a research field, industry never *really* got it
> under control).

I agree with Magus, but measuring in-host (or in-switch) timing is
still possible.  The research team I am with presented a paper at
ISPCS this year on the measuring of in-host latencies and looking at
where packet timestamps take place, such as SO_TIMESTAMP as Magnus
mentions below.  I will point you to a link to our docs, email me off
the list if you do not have access to the IEEE online journals.  The
paper is mainly focused on BSD systems; however, BSD is not unheard of
in the switch world so maybe it can give you a few tricks for what you
want to accomplish regarding your in-switch timing.
Paper: "Probing the Latencies of Software Timestamping"
http://www.synclab.org/docs/

>> I personally have also used endace products to measure packet timings for
>> research, but I didn't need so much precision for that work - however I can
>> say they have a good API and decent tech support for interacting with their
>> cards and products.
>
> Is there native support with Linux kernels?
> It would be very nice to have the support using SO_TIMESTAMP and friends.

Our team also uses Endace.  But we only host the Endcace DAG cards on
our BSD boxes.

-Matt

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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Magnus Danielson]

Erich,

On 12/02/2012 08:54 PM, Erich Heine wrote:

Jonathan,

My research group has had some good experiences using products from Endace (
http://www.endace.com/) for network timing measurement at the ethernet
level. I don't have a pointer immediately to the work, but if there is
interest can ask tomorrow at work. The gist of it though was to understand
precise timing characteristics of network switches for better simulation.
Examining the time "in switch" for various packets at the microsecond level
was needed to understand various delay curves for different network loads,
with an ultimate goal of proper statistical modeling reflecting reality as
close as possible.


This is a bold challenge, it's a difficult task (clear speak: there is a 
reason for this to be a research field, industry never *really* got it 
under control).



I personally have also used endace products to measure packet timings for
research, but I didn't need so much precision for that work - however I can
say they have a good API and decent tech support for interacting with their
cards and products.


Is there native support with Linux kernels?
It would be very nice to have the support using SO_TIMESTAMP and friends.

Cheers,
Magnus

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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Erich Heine]

Jonathan,

My research group has had some good experiences using products from Endace (
http://www.endace.com/) for network timing measurement at the ethernet
level. I don't have a pointer immediately to the work, but if there is
interest can ask tomorrow at work. The gist of it though was to understand
precise timing characteristics of network switches for better simulation.
Examining the time "in switch" for various packets at the microsecond level
was needed to understand various delay curves for different network loads,
with an ultimate goal of proper statistical modeling reflecting reality as
close as possible.

I personally have also used endace products to measure packet timings for
research, but I didn't need so much precision for that work - however I can
say they have a good API and decent tech support for interacting with their
cards and products.

HTH.

Regards,
Erich


On Sat, Dec 1, 2012 at 2:35 PM, Jonatan Walck  wrote:

> -BEGIN PGP SIGNED MESSAGE-
> Hash: SHA1
>
> Eric, your experiences here is of great interest to me too, I've been
> exploring external clocking of Ethernet controllers as of late but
> have not dived into it yet.
>
> I'm more interested in your how, but of course also in your why.
>
> // jwalck
>
> PS. Hey everyone, new to this list since two days joining after
> attending my first PTTI. Working with time and frequency distribution
> in Sweden and with time getting deeper into the field both on and off
> work.
>
> On 12/01/2012 01:15 AM, Eric Garner wrote:
> > I've never done it using to the RTC crystal, but I  do it quite
> > frequently in my Day Job to Ethernet controllers on those same pc
> > mother boards.
> >
> > -Eric
> >
> > On Fri, Nov 30, 2012 at 4:10 PM, Sarah White 
> > wrote:
> >
> >> On 11/30/2012 6:30 PM, Eric Garner wrote:
> >>> the actual RTC on modern (Intel based) PC's is driven from a
> >>> standard 32,768 Hz crystal attached to the PCH. some of them
> >>> are in incredibly
> >> small
> >>> packages now instead of the old tuning fork-in-a-can ones.
> >>> peeling off
> >> the
> >>> load caps and crystal from the board would allow you plenty of
> >>> spaces to tack down a lead from an external synthesizer.
> >>
> >> Yeah, the one on the (Soekis) example was pretty small. So far
> >> none of of the replies have indicated that anyone on here has
> >> experience beyond an embedded system.
> >>
> >> Mostly I started this thread because there have been a few with
> >> people discussing implementing NTP on embedded microcontrollers,
> >> arduino, etc. and I was thinking of doing it from the other side
> >> (turning a nice-ish server into a rock-solid timekeeper)
> >>
> >> Thanks so far everyone. Really impressed that I already managed
> >> to get 4x replies so quickly :)
> >>
> >>
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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Bob Camp]

Hi

Strange - I must indeed have been lucky on the last dozen or so systems I built 
up.

Bob

On Dec 2, 2012, at 1:14 PM, David  wrote:

> On Sun, 2 Dec 2012 08:43:39 -0500, Bob Camp  wrote:
> 
>> Hi
>> 
>> Maybe I'm just shopping in the right places. I have yet to build up a 
>> desktop machine that does *not* have at least one COM port on the 
>> motherboard. That's been true all the way from simple little Atom based ITX 
>> boards right through monster boards with all sorts of crazy stuff on them.  
>> Yes, it's not out the back, but that's very easy to take care of if you need 
>> the port. 
>> 
>> Laptops are a bit different. They seem to die of some sort of display issue 
>> long before a desktop. I don't use them in test setups.
>> 
>> Bob
> 
> When I built my most recent workstation a couple years ago, I
> specifically looked for motherboards that included a COM port and
> thought I had found one but when it arrived, I discovered that they
> left off everything except the UART which was integrated.  Instead of
> trying to figure out what level translator they used, I just bought a
> PCI serial card instead.  None of the USB serial dongles I tried
> worked well.
> 
> I have stopped using laptops as well.  They are too fragile even when
> just sitting in one place.  I have seen a lot of old used working ones
> for sale at HAM swap meets though that are inexpensive.
> 
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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[David]

On Sun, 2 Dec 2012 08:43:39 -0500, Bob Camp  wrote:

>Hi
>
>Maybe I'm just shopping in the right places. I have yet to build up a desktop 
>machine that does *not* have at least one COM port on the motherboard. That's 
>been true all the way from simple little Atom based ITX boards right through 
>monster boards with all sorts of crazy stuff on them.  Yes, it's not out the 
>back, but that's very easy to take care of if you need the port. 
>
>Laptops are a bit different. They seem to die of some sort of display issue 
>long before a desktop. I don't use them in test setups.
>
>Bob

When I built my most recent workstation a couple years ago, I
specifically looked for motherboards that included a COM port and
thought I had found one but when it arrived, I discovered that they
left off everything except the UART which was integrated.  Instead of
trying to figure out what level translator they used, I just bought a
PCI serial card instead.  None of the USB serial dongles I tried
worked well.

I have stopped using laptops as well.  They are too fragile even when
just sitting in one place.  I have seen a lot of old used working ones
for sale at HAM swap meets though that are inexpensive.

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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Bob Camp]

Hi

Maybe I'm just shopping in the right places. I have yet to build up a desktop 
machine that does *not* have at least one COM port on the motherboard. That's 
been true all the way from simple little Atom based ITX boards right through 
monster boards with all sorts of crazy stuff on them.  Yes, it's not out the 
back, but that's very easy to take care of if you need the port. 

Laptops are a bit different. They seem to die of some sort of display issue 
long before a desktop. I don't use them in test setups.

Bob

On Dec 1, 2012, at 11:37 PM, David  wrote:

> On Sat, 01 Dec 2012 19:10:54 -0800, Hal Murray
>  wrote:
> 
>> davidwh...@gmail.com said:
>>> One of my favorite tricks back when the ISA bus was still available was to
>>> use a custom expansion board I built and an oscilloscope to measure the
>>> interrupt latency. 
>> 
>> You can do the same trick without special hardware.  Use the printer port.  
>> Of course, that assumes your PC/Laptop still has a printer port.
> 
> I almost always end up installing a PCI/PCIe serial and parallel
> expansion card into my systems even now.
> 
>> I have a laptop with a printer port on the thing Dell calls a MediaBase.  
>> It's an extender/fattener that includes a CD drive with connectors for 
>> printer port and serial port.  It plugs into a big connector on the bottom 
>> of 
>> the laptop.
>> 
>> Many laptops plug into docking stations for use at a desk.  Sometimes/often 
>> they have printer ports and/or serial ports.
>> 
>> You could probably do it with just a serial port by flapping one of the 
>> output modem control signals.
> 
> I could not always depend on having access to built in serial or
> parallel ports.  These days of course both are pretty much deprecated
> in favor of USB which is useless for this type of work.
> 
>> If you don't have a printer port or serial port, how are you getting the 
>> interrupt into your box?
> 
> Since this was back in the ISA days, I had access to the whole ISA bus
> including the interrupts.  I never built a version for PCI but I did
> consider it.
> 
> The card I built had a pair of 8254 timers, hexadecimal display,
> keypad, a bunch of auxiliary I/O, and all of the decoding to use it. I
> usually end up building something similar for microcontroller projects
> that operates via SPI although serial to a PC running a terminal
> program is often better.
> 
>> Many years ago, I helped a friend with this sort of thing.  We were working 
>> for DEC back in the days before Intel had captured everything and 
>> workstations still needed lots of chips and chips had big pins so you could 
>> get a scope probe on them.  My part was to connect scope probes to the 
>> interrupt line from the ethernet chip and the chip select for the MAC 
>> address 
>> ROM.  He patched the driver's interrupt routine to read the ROM.
> 
> I have also done that on occasion and sometimes still do.  Usually I
> solder a little grab point for the probe into place.  Sometimes I will
> just add a resistor or transistor buffer depending on impedance issues
> and an RG-316 pigtail.
> 
> The funny part is that back then, I was using one of the early
> Tektronix series TDS oscilloscopes.  Now I do the same thing with an
> older Tektronix 2230, 2232, or 2440 series oscilloscope and I have a
> word recognizer for my 2440 which works surprisingly well.  At some
> point, I need to pick up a DSO that supports variable and infinite
> persistence.
> 
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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[David]

On Sat, 01 Dec 2012 19:10:54 -0800, Hal Murray
 wrote:

>davidwh...@gmail.com said:
>> One of my favorite tricks back when the ISA bus was still available was to
>> use a custom expansion board I built and an oscilloscope to measure the
>> interrupt latency. 
>
>You can do the same trick without special hardware.  Use the printer port.  
>Of course, that assumes your PC/Laptop still has a printer port.

I almost always end up installing a PCI/PCIe serial and parallel
expansion card into my systems even now.

>I have a laptop with a printer port on the thing Dell calls a MediaBase.  
>It's an extender/fattener that includes a CD drive with connectors for 
>printer port and serial port.  It plugs into a big connector on the bottom of 
>the laptop.
>
>Many laptops plug into docking stations for use at a desk.  Sometimes/often 
>they have printer ports and/or serial ports.
>
>You could probably do it with just a serial port by flapping one of the 
>output modem control signals.

I could not always depend on having access to built in serial or
parallel ports.  These days of course both are pretty much deprecated
in favor of USB which is useless for this type of work.

>If you don't have a printer port or serial port, how are you getting the 
>interrupt into your box?

Since this was back in the ISA days, I had access to the whole ISA bus
including the interrupts.  I never built a version for PCI but I did
consider it.

The card I built had a pair of 8254 timers, hexadecimal display,
keypad, a bunch of auxiliary I/O, and all of the decoding to use it. I
usually end up building something similar for microcontroller projects
that operates via SPI although serial to a PC running a terminal
program is often better.

>Many years ago, I helped a friend with this sort of thing.  We were working 
>for DEC back in the days before Intel had captured everything and 
>workstations still needed lots of chips and chips had big pins so you could 
>get a scope probe on them.  My part was to connect scope probes to the 
>interrupt line from the ethernet chip and the chip select for the MAC address 
>ROM.  He patched the driver's interrupt routine to read the ROM.

I have also done that on occasion and sometimes still do.  Usually I
solder a little grab point for the probe into place.  Sometimes I will
just add a resistor or transistor buffer depending on impedance issues
and an RG-316 pigtail.

The funny part is that back then, I was using one of the early
Tektronix series TDS oscilloscopes.  Now I do the same thing with an
older Tektronix 2230, 2232, or 2440 series oscilloscope and I have a
word recognizer for my 2440 which works surprisingly well.  At some
point, I need to pick up a DSO that supports variable and infinite
persistence.

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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Hal Murray]

davidwh...@gmail.com said:
> One of my favorite tricks back when the ISA bus was still available was to
> use a custom expansion board I built and an oscilloscope to measure the
> interrupt latency. 

You can do the same trick without special hardware.  Use the printer port.  
Of course, that assumes your PC/Laptop still has a printer port.

I have a laptop with a printer port on the thing Dell calls a MediaBase.  
It's an extender/fattener that includes a CD drive with connectors for 
printer port and serial port.  It plugs into a big connector on the bottom of 
the laptop.

Many laptops plug into docking stations for use at a desk.  Sometimes/often 
they have printer ports and/or serial ports.

You could probably do it with just a serial port by flapping one of the 
output modem control signals.

If you don't have a printer port or serial port, how are you getting the 
interrupt into your box?

--

Many years ago, I helped a friend with this sort of thing.  We were working 
for DEC back in the days before Intel had captured everything and 
workstations still needed lots of chips and chips had big pins so you could 
get a scope probe on them.  My part was to connect scope probes to the 
interrupt line from the ethernet chip and the chip select for the MAC address 
ROM.  He patched the driver's interrupt routine to read the ROM.


-- 
These are my opinions.  I hate spam.




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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[David]

On Sun, 02 Dec 2012 01:53:07 +0100, Magnus Danielson
 wrote:

>On 12/02/2012 01:29 AM, David wrote:
>> Originally the IBM PC design used an 8253 or 8254 PIT, programmable
>> interval timer, located at ports 40h to 43h with Timer 0 clocked at
>> 1.193182 MHz (1/3rd of 3.579545 MHz or 1/12th of 14.318 MHz) and set
>> to divide by 65536 which generated about an 18.2 Hz interrupt rate on
>> IRQ 0.  Timer 1 generated the since deprecated DRAM refresh clock and
>> Timer 2 goes to the PC speaker.
>
>In a modern world, look for things like HPET and TSC:
>
>http://en.wikipedia.org/wiki/High_Precision_Event_Timer
>http://en.wikipedia.org/wiki/Time_Stamp_Counter
>
>You want to get a better reference clock to these timers.
>
>Cheers,
>Magnus

I only mention and do not go into detail about the higher precision
timers later in my post because by the time they were available,
Intel's system management mode was adding so much jitter than I lost
interest in using PC hardware in applications where they otherwise
might have been useful.  To be fair, not all motherboards and BIOSes
had this problem but it was not worth weeding out the poorly
performing ones.

One of my favorite tricks back when the ISA bus was still available
was to use a custom expansion board I built and an oscilloscope to
measure the interrupt latency.

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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Magnus Danielson]

On 12/02/2012 01:29 AM, David wrote:

Originally the IBM PC design used an 8253 or 8254 PIT, programmable
interval timer, located at ports 40h to 43h with Timer 0 clocked at
1.193182 MHz (1/3rd of 3.579545 MHz or 1/12th of 14.318 MHz) and set
to divide by 65536 which generated about an 18.2 Hz interrupt rate on
IRQ 0.  Timer 1 generated the since deprecated DRAM refresh clock and
Timer 2 goes to the PC speaker.


In a modern world, look for things like HPET and TSC:

http://en.wikipedia.org/wiki/High_Precision_Event_Timer
http://en.wikipedia.org/wiki/Time_Stamp_Counter

You want to get a better reference clock to these timers.

Cheers,
Magnus

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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[David]

Originally the IBM PC design used an 8253 or 8254 PIT, programmable
interval timer, located at ports 40h to 43h with Timer 0 clocked at
1.193182 MHz (1/3rd of 3.579545 MHz or 1/12th of 14.318 MHz) and set
to divide by 65536 which generated about an 18.2 Hz interrupt rate on
IRQ 0.  Timer 1 generated the since deprecated DRAM refresh clock and
Timer 2 goes to the PC speaker.

Some of the early IBM PC non-compatible hardware implemented a fixed
divisor for Timer 0 which caused problems for software expecting to be
able to reprogram the divider.

I do not know how they generate the 1.193182 MHz PIT clock now.  Early
on they just used an additional oscillator, usually 14.318 MHz, which
was separate from the CPU clock.  I lost interest and started doing
all of my precision timer functions in external hardware when Intel's
SMM, system management mode, started adding unacceptable jitter to
interrupt service routines.

Now of course a variety of higher precision timers are included.
Either the 1.193182 MHz based PIT via interrupt 0 or the 32.768 kHz
based RTC via interrupt 8 can be used to calibrate the CPU timers when
the CPU clock is unknown.

There was a hoax at about the time that the 12 MHz 286 microprocessors
became available where a couple of guys were wiring a small capacitor
across the 32.768 kHz clock crystal causing the RTC to run slow which
caused the CPU clock speed measured via software to appear many times
higher.  Conveniently the wall clock time as measured by the now
slowed RTC showed the same thing.  I remember an interview the guys
gave where they declined to describe their improvements to the 286 but
said the process amounted to collecting groups of instructions and
ramming them through as fast as possible and that it might be feasible
with a 386 as well.

On Sat, 1 Dec 2012 12:34:43 -0700, "Mark Allwright"
 wrote:

>You need to replace the clock that drives the CPU; in some designs this was 
>the 14.318 MHz oscillator that would be multiplied up to the required 
>frequency.  You could also replace the 14.318 MHz oscillator with a TCXO or 
>better; make your own simple OCXO around a 14.318 MHz oscillator or lock a 
>14.318 MHz oscillator to a high stability reference oscillator (Rb, GPSDO 
>etc.).  You would need to do some circuit surgery on the PC motherboard for 
>this type of stuff.
>
>Some links:
>
> Lock 14.318 MHz to Rb
> Simple oven
> More simple oven circuits
> John's note for the Soekris 
>and clock hacking
>
>Regards.
>
>Mark.

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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Jonatan Walck]

-BEGIN PGP SIGNED MESSAGE-
Hash: SHA1

Eric, your experiences here is of great interest to me too, I've been
exploring external clocking of Ethernet controllers as of late but
have not dived into it yet.

I'm more interested in your how, but of course also in your why.

// jwalck

PS. Hey everyone, new to this list since two days joining after
attending my first PTTI. Working with time and frequency distribution
in Sweden and with time getting deeper into the field both on and off
work.

On 12/01/2012 01:15 AM, Eric Garner wrote:
> I've never done it using to the RTC crystal, but I  do it quite
> frequently in my Day Job to Ethernet controllers on those same pc
> mother boards.
> 
> -Eric
> 
> On Fri, Nov 30, 2012 at 4:10 PM, Sarah White 
> wrote:
> 
>> On 11/30/2012 6:30 PM, Eric Garner wrote:
>>> the actual RTC on modern (Intel based) PC's is driven from a
>>> standard 32,768 Hz crystal attached to the PCH. some of them
>>> are in incredibly
>> small
>>> packages now instead of the old tuning fork-in-a-can ones.
>>> peeling off
>> the
>>> load caps and crystal from the board would allow you plenty of
>>> spaces to tack down a lead from an external synthesizer.
>> 
>> Yeah, the one on the (Soekis) example was pretty small. So far
>> none of of the replies have indicated that anyone on here has
>> experience beyond an embedded system.
>> 
>> Mostly I started this thread because there have been a few with
>> people discussing implementing NTP on embedded microcontrollers,
>> arduino, etc. and I was thinking of doing it from the other side
>> (turning a nice-ish server into a rock-solid timekeeper)
>> 
>> Thanks so far everyone. Really impressed that I already managed
>> to get 4x replies so quickly :)
>> 
>> 
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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Mark Allwright]

You need to replace the clock that drives the CPU; in some designs this was 
the 14.318 MHz oscillator that would be multiplied up to the required 
frequency.  You could also replace the 14.318 MHz oscillator with a TCXO or 
better; make your own simple OCXO around a 14.318 MHz oscillator or lock a 
14.318 MHz oscillator to a high stability reference oscillator (Rb, GPSDO 
etc.).  You would need to do some circuit surgery on the PC motherboard for 
this type of stuff.


Some links:

<http://www.moshier.net/#Rubid_pc> Lock 14.318 MHz to Rb
<http://www.wraith.sf.ca.us/ntp/#ocxo-osc> Simple oven
<http://www.techlib.com/electronics/ovenckts.htm> More simple oven circuits
<http://www.febo.com/pages/soekris/index.html> John's note for the Soekris 
and clock hacking


Regards.

Mark.

--

Mark Allwright, VE6NTP

-Original Message- 
From: Sarah White

Sent: Friday, November 30, 2012 5:10 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Using a frequency synthesizer replacement for 
motherboard oscillator


On 11/30/2012 6:30 PM, Eric Garner wrote:

the actual RTC on modern (Intel based) PC's is driven from a standard
32,768 Hz crystal attached to the PCH. some of them are in incredibly 
small

packages now instead of the old tuning fork-in-a-can ones. peeling off the
load caps and crystal from the board would allow you plenty of spaces to
tack down a lead from an external synthesizer.


Yeah, the one on the (Soekis) example was pretty small. So far none of
of the replies have indicated that anyone on here has experience beyond
an embedded system.

Mostly I started this thread because there have been a few with people
discussing implementing NTP on embedded microcontrollers, arduino, etc.
and I was thinking of doing it from the other side (turning a nice-ish
server into a rock-solid timekeeper)

Thanks so far everyone. Really impressed that I already managed to get
4x replies so quickly :)



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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Poul-Henning Kamp]

In message , Bob Camp writes:

>It's most commonly done with things like a Soekris 45xx series board. You
>don't need anything very exotic for the frequency conversion. The jitter in 
>the PC is way worse than what the external chips will be creating. 

Actually that is _not_ true anymore.  Modern CPU's are very finicky about
clock jitter because the PLL the frequency up to GHz range.  Some of the
clock-chips used now discipline a low-UHF range oscillator to the XTAL
to cope with this, but most just PLL the frequency up there.

>The real question is - what is the "magic frequency" on the particular 
>mother board you are going to modify? Once upon a time they all were a pretty
>predictable 14.xxx MHz. These days, who knows what's going in where

It's pretty much still 14.318 Mhz pretty universally.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Chris Albertson]

On Fri, Nov 30, 2012 at 8:39 PM, David I. Emery wrote:

> On Fri, Nov 30, 2012 at 09:58:29PM -0500, Bob Camp wrote:
> > Hi
> >
>
> > The problem just the clock it's also the operating system. If it's not
> > designed with timing in mind (= it's an RTOS at some level) then you
> > will have sloppy timing.


What is "sloppy timing"?   If about 10 microseconds of error is "sloppy"
then you are right.

None of the effects you describe need to cause a problem.   Even on a
non-RTOS the limiting factor is the uncertainty in the interrupt latency.
 The way it works is that the PPS interrupts the CPU and then inside the
handler a hardware counter is sampled and stored and that is it.   Nothing
else needs to occur in real time.

Quite a few people are able to run NTP serversand keep there system clocks
for small (uSecs) error from UTC.But now the question is if an
application program can us the clock .without some error  I think it can.
A simple example is a program that time stamps data.   It waits for data
then when it comes in reads the system clock then tags the data with the
sampled clock.   The problem is if the CPU is taken away.   One way to
detect a problem is to read the clock twice and check for a deta time of
more than a few nanoseconds.  Then if you read the data between those to
clock samples you will know the clock was acuratly sampled.

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[David I. Emery]

On Fri, Nov 30, 2012 at 09:58:29PM -0500, Bob Camp wrote:
> Hi
> 

> The problem just the clock it's also the operating system. If it's not
> designed with timing in mind (= it's an RTOS at some level) then you
> will have sloppy timing. Counters can help, but they are not the entire
> solution. If your email (or anti-virus or ...) program can pop up and
> monopolize the cpu for a chunk of a second (as in 10's or 100's of ms), 
> precision timing isn't going to work very well. There's only so much you
> can do after the fact. If the pps edge was supposed to go out 27 ms ago,
> and you only got control back now, you are out of luck. 

No doubt that you get into a sort of philosophic meaning of 
what-really-is-now relativity here... if parts of the kernel know what
time it is quite precisely but other parts and most user programs are
only loosely aware of and only able to react to it post facto by large 
and jittery intervals, what is the meaning of microsecond or even ns
level OS time sync ?

Most modern kernels *internally* have at least some degree of
fairly serious real time high priority tight deadline stuff going on -
and API hooks for accessing it available - the degree to which this is
exposed and visible to or usable by user space threads varies a lot, and
correctly using this stuff always requires pretty deep skill and
thought.  Not for the faint of heart or inexperienced.   Very easy to
make subtle errors that cause bugs that happen only once every few
hundred or even many thousands of hours.

And pretty obviously the more control and access the user (eg
applications programmers) get and use the less likely it is that some
combination of separately developed and architected applications and a
particular kernel running on particular hardware will handle all of this
right ALL the time.   Emphasis here on ALL, it usually works most of the
time but making it essentially never fail is really really hard.  And
many of those failures result in things like deadly embrace lockups
which can cause everything to stop or rare conditions in which apparent
causality and temporal coherence completely inverts and things which
"cannot happen" happen exposing all kinds of reasonable but not
quite bulletproof assumptions.


-- 
  Dave Emery N1PRE/AE, d...@dieconsulting.com  DIE Consulting, Weston, Mass 
02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in 
celebration of what could have been, but wasn't and is not to be now either."


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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Bob Camp]

Hi

The problem just the clock it's also the operating system. If it's not designed 
with timing in mind (= it's an RTOS at some level) then you will have sloppy 
timing. Counters can help, but they are not the entire solution. If your email 
(or anti-virus or ...) program can pop up and monopolize the cpu for a chunk of 
a second (as in 10's or 100's of ms),  precision timing isn't going to work 
very well. There's only so much you can do after the fact. If the pps edge was 
supposed to go out 27 ms ago, and you only got control back now, you are out of 
luck. 

Bob

On Nov 30, 2012, at 9:19 PM, David I. Emery  wrote:

> On Fri, Nov 30, 2012 at 04:24:38PM -0600, shali...@gmail.com wrote:
>> I am not sure that a precision clock will help if the cpu is busy and skips 
>> clock cycles. I believe this is one of the problems with general purpose 
>> OSes like Windows.
>> 
>> I believe the better boards like the Soekis use hardware dividers to 
>> alleviate the cpu busy problem.
>> 
>> Didier
> 
>   For what it is worth, for many generations now all major CPUs
> have had kernel software readable nanosecond level time of day time
> stamping counters that are clocked from the incoming clock to the CPU
> chip and run continuously and steadily without skipped or added ticks
> whatever the CPU is doing.   And in addition to these time stamping
> counters, most all CPU chip sets also include "real time clock"
> interrupts which again are  driven off of continuously counting counters
> referenced to the clock input to the CPU and can be programmed to
> interrupt ever n ticks of the master clock - regardless of CPU activity.
> 
>   Obviously while servicing the real time clock interrupts is
> usually a very high priority, depending on how the OS works and what
> privileges real time priority apps have occasionally a real time
> interrupt can be serviced so slowly that another one happens before it
> is cleared.   Some OS real time clock handlers attempt to spot these
> cases and adjust their idea of time to compensate.
> 
>   Any OS based PLL driven by time stamping 1 PPS timing interrupts
> WILL see some jitter in its time stamps due to bus and internal CPU
> latencies and use of interrupt off intervals to protect against race
> conditions. This noise is unavoidable and does depend on CPU load and
> even  how fast the CPU clocks are set to run at any instant (modern CPUS
> dynamically adjust clock rate in various areas of their logic to
> conserve power and reduce heat).
> 
>   So for a very fine control a hardware based 1PPS event time
> stamper will provide greater accuracy and less jitter, especially if it
> is driven by a high accuracy external clock source locked to some time
> reference.
> 
>   But of course it IS  useful to clock the CPU with an accurate
> clock as that then means the internal CPU time stamp counter and real
> time tick interrupt is ticking at a known rate - starting from some
> epoch that can be eventually calibrated over time - and multiple 1 PPS
> ticks - within a few ns or so of 1 PPS GPS or other similar time.
> 
>   If the CPU clock is unstable and wanders around with time,
> temperature, power and fan activity it then becomes necessary - as the
> timing 1PPS PLLs built into many modern kernels do - to try to measure
> its frequency error and drift and estimate the error phase between it
> and true time. If the CPU clock  is locked to a reference, this is not
> as hard a thing to do as the only relative unknown is when exactly the
> zero epoch on the counter occurred.
> 
> 
> -- 
>  Dave Emery N1PRE/AE, d...@dieconsulting.com  DIE Consulting, Weston, Mass 
> 02493
> "An empty zombie mind with a forlorn barely readable weatherbeaten
> 'For Rent' sign still vainly flapping outside on the weed encrusted pole - in 
> celebration of what could have been, but wasn't and is not to be now either."
> 
> 
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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[David I. Emery]

On Fri, Nov 30, 2012 at 04:24:38PM -0600, shali...@gmail.com wrote:
> I am not sure that a precision clock will help if the cpu is busy and skips 
> clock cycles. I believe this is one of the problems with general purpose OSes 
> like Windows.
> 
> I believe the better boards like the Soekis use hardware dividers to 
> alleviate the cpu busy problem.
> 
> Didier

For what it is worth, for many generations now all major CPUs
have had kernel software readable nanosecond level time of day time
stamping counters that are clocked from the incoming clock to the CPU
chip and run continuously and steadily without skipped or added ticks
whatever the CPU is doing.   And in addition to these time stamping
counters, most all CPU chip sets also include "real time clock"
interrupts which again are  driven off of continuously counting counters
referenced to the clock input to the CPU and can be programmed to
interrupt ever n ticks of the master clock - regardless of CPU activity.

Obviously while servicing the real time clock interrupts is
usually a very high priority, depending on how the OS works and what
privileges real time priority apps have occasionally a real time
interrupt can be serviced so slowly that another one happens before it
is cleared.   Some OS real time clock handlers attempt to spot these
cases and adjust their idea of time to compensate.

Any OS based PLL driven by time stamping 1 PPS timing interrupts
WILL see some jitter in its time stamps due to bus and internal CPU
latencies and use of interrupt off intervals to protect against race
conditions. This noise is unavoidable and does depend on CPU load and
even  how fast the CPU clocks are set to run at any instant (modern CPUS
dynamically adjust clock rate in various areas of their logic to
conserve power and reduce heat).

So for a very fine control a hardware based 1PPS event time
stamper will provide greater accuracy and less jitter, especially if it
is driven by a high accuracy external clock source locked to some time
reference.

But of course it IS  useful to clock the CPU with an accurate
clock as that then means the internal CPU time stamp counter and real
time tick interrupt is ticking at a known rate - starting from some
epoch that can be eventually calibrated over time - and multiple 1 PPS
ticks - within a few ns or so of 1 PPS GPS or other similar time.

If the CPU clock is unstable and wanders around with time,
temperature, power and fan activity it then becomes necessary - as the
timing 1PPS PLLs built into many modern kernels do - to try to measure
its frequency error and drift and estimate the error phase between it
and true time. If the CPU clock  is locked to a reference, this is not
as hard a thing to do as the only relative unknown is when exactly the
zero epoch on the counter occurred.


-- 
  Dave Emery N1PRE/AE, d...@dieconsulting.com  DIE Consulting, Weston, Mass 
02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in 
celebration of what could have been, but wasn't and is not to be now either."


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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Sarah White]

On 11/30/2012 7:54 PM, John Ackermann N8UR wrote:
> On Nov 30, 2012, at 7:10 PM, Sarah White  wrote:
> 
>> On 11/30/2012 6:30 PM, Eric Garner wrote:
>>> the actual RTC on modern (Intel based) PC's is driven from a standard
>>> 32,768 Hz crystal attached to the PCH. some of them are in incredibly small
>>> packages now instead of the old tuning fork-in-a-can ones. peeling off the
>>> load caps and crystal from the board would allow you plenty of spaces to
>>> tack down a lead from an external synthesizer.
>>
>> Yeah, the one on the (Soekis) example was pretty small. So far none of
>> of the replies have indicated that anyone on here has experience beyond
>> an embedded system.
> 
> Sarah, when I was designing and protoyping the ClockBlock, I did interface it 
> with a standard mobo (don't recall the specifics).  As someone else pointed 
> out, the process is basically:
> 
> 1.  Find and remove the oscillator that drives the CPU, likely something 
> between 33 and 100 Mhz in modern systems.  It's *not* the 32.768 kHz crystal 
> (if there still is one; I think it's actually built into thr RTC chip these 
> days).
> 
> 2.  Figure out which pin is the output of the oscillator module.
> 
> 3.  Figure out the proper drive voltage (most easily based on the supply 
> voltage of the oscillator).
> 
> 4.  Hook the ClockBlock output to the signal pad where the oscillator used to 
> be via small-diameter coax cable such as RG-174, connecting the coax shield 
> to ground on the board and using a series resistor if you need to drop the 
> signal voltage below the 3.3V minimum that the ClockBlock can provide via its 
> voltage-select jumper.  Some math and/or experimentation may be involved; the 
> goal is to get enough signal to drive the board, without exceeding the safe 
> Vin rsting of whatever devices the clock is driving.
> 
> 5.  Set the ClockBlock jumpers for the proper clock frequency.
> 
> Have fun!
> 
> John

John :)

Ok, wow, thanks!

I couldn't have asked for a better answer to my specific question than
one from the designer of the module itself (and more or less saying, and
confirming "yes, I've done this in testing")

Slightly unrelated but...

Any chance you could recommend a minimalist set of tools that would be
helpful for poking around so I could make sure things are wired up right
/ signaling as desired, etc?

Please don't say "logic analyzer" or "oscilloscope" because if that sort
of thing is mandatory, I'll just give up now.

I took a basic electrical engineering course nearly 20 years ago, and
have worked on a few simple controllers and even modified a computer
motherboard or two, so this won't be my first venture into such things.

... I'm just currently without ANY tools. (Not counting the dremmel
rotory tool for doing acrylic fingernails, and/or various repair &
tooling, cutting, and sanding of things that would take too long by hand)

... Well mostly none. The only decent tool I have on hand is a soldering
iron with a variable control / stand to adjust power and to have
somewhere to sit it while it warms up (also, there's a position on the
stand which is handy for holding the iron stationary so I can tin wires)

Guess that's all for now. Thanks everyone :)

P.S. Probably not doing anything like this for at least a month anyway.
Still need to sock away enough budget for "cheap computer to modify" and
the clock block itself (or some other appropriate frequency synthesizer)

P.P.S This might be my last post of the night. Friend's birthday is
today / have a party to finish getting things ready for.

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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Jim Lux]

On 11/30/12 4:58 PM, John Ackermann N8UR wrote:

On Nov 30, 2012, at 7:42 PM, John Ackermann  N8UR  wrote:


In this case, you're not looking for the RTC but rather the clock that drives 
the COU


Read "CPU".  Stupid iPad keyboard.



I was wondering.. Clock Oscillator Unit? Cryptic Obfuscated Unknown?



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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Jim Welch]

OK, I'll bite.  Why?

Jim

>>>I've never done it using to the RTC crystal, but I  do it quite
frequently in my Day Job to >>>Ethernet controllers on those same pc mother
boards.
>>>
>>>-Eric

On Fri, Nov 30, 2012 at 4:10 PM, Sarah White  wrote:

> On 11/30/2012 6:30 PM, Eric Garner wrote:
> > the actual RTC on modern (Intel based) PC's is driven from a 
> > standard
> > 32,768 Hz crystal attached to the PCH. some of them are in 
> > incredibly
> small
> > packages now instead of the old tuning fork-in-a-can ones. peeling 
> > off
> the
> > load caps and crystal from the board would allow you plenty of 
> > spaces to tack down a lead from an external synthesizer.
>
> Yeah, the one on the (Soekis) example was pretty small. So far none of 
> of the replies have indicated that anyone on here has experience 
> beyond an embedded system.
>
> Mostly I started this thread because there have been a few with people 
> discussing implementing NTP on embedded microcontrollers, arduino, etc.
> and I was thinking of doing it from the other side (turning a nice-ish 
> server into a rock-solid timekeeper)
>
> Thanks so far everyone. Really impressed that I already managed to get 
> 4x replies so quickly :)
>
>
>
> ___
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> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>



-- 
--Eric
_
Eric Garner
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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[John Ackermann N8UR]

On Nov 30, 2012, at 7:42 PM, John Ackermann  N8UR  wrote:

> In this case, you're not looking for the RTC but rather the clock that drives 
> the COU

Read "CPU".  Stupid iPad keyboard.
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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[John Ackermann N8UR]

On Nov 30, 2012, at 7:10 PM, Sarah White  wrote:

> On 11/30/2012 6:30 PM, Eric Garner wrote:
>> the actual RTC on modern (Intel based) PC's is driven from a standard
>> 32,768 Hz crystal attached to the PCH. some of them are in incredibly small
>> packages now instead of the old tuning fork-in-a-can ones. peeling off the
>> load caps and crystal from the board would allow you plenty of spaces to
>> tack down a lead from an external synthesizer.
> 
> Yeah, the one on the (Soekis) example was pretty small. So far none of
> of the replies have indicated that anyone on here has experience beyond
> an embedded system.

Sarah, when I was designing and protoyping the ClockBlock, I did interface it 
with a standard mobo (don't recall the specifics).  As someone else pointed 
out, the process is basically:

1.  Find and remove the oscillator that drives the CPU, likely something 
between 33 and 100 Mhz in modern systems.  It's *not* the 32.768 kHz crystal 
(if there still is one; I think it's actually built into thr RTC chip these 
days).

2.  Figure out which pin is the output of the oscillator module.

3.  Figure out the proper drive voltage (most easily based on the supply 
voltage of the oscillator).

4.  Hook the ClockBlock output to the signal pad where the oscillator used to 
be via small-diameter coax cable such as RG-174, connecting the coax shield to 
ground on the board and using a series resistor if you need to drop the signal 
voltage below the 3.3V minimum that the ClockBlock can provide via its 
voltage-select jumper.  Some math and/or experimentation may be involved; the 
goal is to get enough signal to drive the board, without exceeding the safe Vin 
rsting of whatever devices the clock is driving.

5.  Set the ClockBlock jumpers for the proper clock frequency.

Have fun!

John




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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[John Ackermann N8UR]

In this case, you're not looking for the RTC but rather the clock that drives 
the COU, which is what drives the system clock.  On most systems, the RTC is 
read only at startup and is not used once the system is running.

John

On Nov 30, 2012, at 6:30 PM, Eric Garner  wrote:

> the actual RTC on modern (Intel based) PC's is driven from a standard
> 32,768 Hz crystal attached to the PCH. some of them are in incredibly small
> packages now instead of the old tuning fork-in-a-can ones. peeling off the
> load caps and crystal from the board would allow you plenty of spaces to
> tack down a lead from an external synthesizer.
> 
> 
> -Eric
> 
> On Fri, Nov 30, 2012 at 3:04 PM, bownes  wrote:
> 
>> It all depends on what clock your talking about. Any given PC probably has
>> more than one oscillator onboard.
>> Generally there will be one for the CPU, one for the display circuitry,
>> and probably one for the real time clock.
>> 
>> Presuming you are talking about the CPU clock, it should be fairly
>> straightforward to find the oscillator package on the motherboard find the
>> pin with clock output and feed your clock input there.
>> 
>> On Nov 30, 2012, at 16:59, Bob Camp  wrote:
>> 
>>> Hi
>>> 
>>> It's most commonly done with things like a Soekris 45xx series board.
>> You don't need anything very exotic for the frequency conversion. The
>> jitter in the PC is way worse than what the external chips will be creating.
>>> 
>>> The real question is - what is the "magic frequency" on the particular
>> mother board you are going to modify? Once upon a time they all were a
>> pretty predictable 14.xxx MHz. These days, who knows what's going in where…
>>> 
>>> Bob
>>> 
>>> On Nov 30, 2012, at 4:55 PM, Sarah White  wrote:
>>> 
 Has anyone ever used a TAPR clock block or other frequency synthesizer
 to sort the clock drift / timing problems on a regular computer? I'll
 probably end up with a used dell or IBM workstation for this purpose.
 
 Recently, I came across a low-cost frequency synthesizer capable of
 using a 10mhz frequency reference (planning on using the thunderbolt
 GPSDO I'm working with once I manage to sort out the temperature issues)
 
 http://www.tapr.org/~n8ur/Clock-Block_Manual.pdf
 
 ^ TAPR "Clock Block" has an installation example for how to do what I'm
 planning with a Soekris net4501 low-cost / low-power embedded device...
 
 What I'm hoping to figure out is how to do the same, except on a proper
 computer such as the local used ones I'm able to get for less than $200
 with 2ghz with 30GB hard disk, 512mb or more ram, etc. So I figure this
 should be fine for what I'm planning.
 
 Example of what I'm trying to do, though based on the low-power embedded
 Soekris net4501 system from the TAPR manual's example section:
 
 http://www.febo.com/time-freq/ntp/soekris/index.html
 
 ^Aren't those the photos from clock block frequency synthesizer manual?
 
 Again, I'm wondering if anyone has opinions or experience about doing
 such things with NOT an embedded system (as I said, can get a nice 2ghz
 or so machine for less than $200 locally at a brick and mortar shop
 within walking distance)
 
 Thanks in advance,
 Sarah
 
 
 ___
 time-nuts mailing list -- time-nuts@febo.com
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>>> 
>>> 
>>> ___
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> 
> 
> 
> -- 
> --Eric
> _
> Eric Garner
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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Bob Camp]

Hi

In the case of the Soekris, it was not the real time clock that we all played 
with. THe clock you fiddle is the CPU clock. The system is running FreeBSD or 
Lunix, so it's a cut above a typical embedded system. A RTOS (like Windows CE) 
will indeed do a bit better with a good CPU clock. Anything like conventional 
Windows will still have issues, even with a good clock.

Bob

On Nov 30, 2012, at 7:10 PM, Sarah White  wrote:

> On 11/30/2012 6:30 PM, Eric Garner wrote:
>> the actual RTC on modern (Intel based) PC's is driven from a standard
>> 32,768 Hz crystal attached to the PCH. some of them are in incredibly small
>> packages now instead of the old tuning fork-in-a-can ones. peeling off the
>> load caps and crystal from the board would allow you plenty of spaces to
>> tack down a lead from an external synthesizer.
> 
> Yeah, the one on the (Soekis) example was pretty small. So far none of
> of the replies have indicated that anyone on here has experience beyond
> an embedded system.
> 
> Mostly I started this thread because there have been a few with people
> discussing implementing NTP on embedded microcontrollers, arduino, etc.
> and I was thinking of doing it from the other side (turning a nice-ish
> server into a rock-solid timekeeper)
> 
> Thanks so far everyone. Really impressed that I already managed to get
> 4x replies so quickly :)
> 
> 
> 
> ___
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> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Eric Garner]

I've never done it using to the RTC crystal, but I  do it quite frequently
in my Day Job to Ethernet controllers on those same pc mother boards.

-Eric

On Fri, Nov 30, 2012 at 4:10 PM, Sarah White  wrote:

> On 11/30/2012 6:30 PM, Eric Garner wrote:
> > the actual RTC on modern (Intel based) PC's is driven from a standard
> > 32,768 Hz crystal attached to the PCH. some of them are in incredibly
> small
> > packages now instead of the old tuning fork-in-a-can ones. peeling off
> the
> > load caps and crystal from the board would allow you plenty of spaces to
> > tack down a lead from an external synthesizer.
>
> Yeah, the one on the (Soekis) example was pretty small. So far none of
> of the replies have indicated that anyone on here has experience beyond
> an embedded system.
>
> Mostly I started this thread because there have been a few with people
> discussing implementing NTP on embedded microcontrollers, arduino, etc.
> and I was thinking of doing it from the other side (turning a nice-ish
> server into a rock-solid timekeeper)
>
> Thanks so far everyone. Really impressed that I already managed to get
> 4x replies so quickly :)
>
>
>
> ___
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> To unsubscribe, go to
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>



-- 
--Eric
_
Eric Garner
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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Sarah White]

On 11/30/2012 6:30 PM, Eric Garner wrote:
> the actual RTC on modern (Intel based) PC's is driven from a standard
> 32,768 Hz crystal attached to the PCH. some of them are in incredibly small
> packages now instead of the old tuning fork-in-a-can ones. peeling off the
> load caps and crystal from the board would allow you plenty of spaces to
> tack down a lead from an external synthesizer.

Yeah, the one on the (Soekis) example was pretty small. So far none of
of the replies have indicated that anyone on here has experience beyond
an embedded system.

Mostly I started this thread because there have been a few with people
discussing implementing NTP on embedded microcontrollers, arduino, etc.
and I was thinking of doing it from the other side (turning a nice-ish
server into a rock-solid timekeeper)

Thanks so far everyone. Really impressed that I already managed to get
4x replies so quickly :)



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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Eric Garner]

the actual RTC on modern (Intel based) PC's is driven from a standard
32,768 Hz crystal attached to the PCH. some of them are in incredibly small
packages now instead of the old tuning fork-in-a-can ones. peeling off the
load caps and crystal from the board would allow you plenty of spaces to
tack down a lead from an external synthesizer.


-Eric

On Fri, Nov 30, 2012 at 3:04 PM, bownes  wrote:

> It all depends on what clock your talking about. Any given PC probably has
> more than one oscillator onboard.
> Generally there will be one for the CPU, one for the display circuitry,
> and probably one for the real time clock.
>
> Presuming you are talking about the CPU clock, it should be fairly
> straightforward to find the oscillator package on the motherboard find the
> pin with clock output and feed your clock input there.
>
> On Nov 30, 2012, at 16:59, Bob Camp  wrote:
>
> > Hi
> >
> > It's most commonly done with things like a Soekris 45xx series board.
> You don't need anything very exotic for the frequency conversion. The
> jitter in the PC is way worse than what the external chips will be creating.
> >
> > The real question is - what is the "magic frequency" on the particular
> mother board you are going to modify? Once upon a time they all were a
> pretty predictable 14.xxx MHz. These days, who knows what's going in where…
> >
> > Bob
> >
> > On Nov 30, 2012, at 4:55 PM, Sarah White  wrote:
> >
> >> Has anyone ever used a TAPR clock block or other frequency synthesizer
> >> to sort the clock drift / timing problems on a regular computer? I'll
> >> probably end up with a used dell or IBM workstation for this purpose.
> >>
> >> Recently, I came across a low-cost frequency synthesizer capable of
> >> using a 10mhz frequency reference (planning on using the thunderbolt
> >> GPSDO I'm working with once I manage to sort out the temperature issues)
> >>
> >> http://www.tapr.org/~n8ur/Clock-Block_Manual.pdf
> >>
> >> ^ TAPR "Clock Block" has an installation example for how to do what I'm
> >> planning with a Soekris net4501 low-cost / low-power embedded device...
> >>
> >> What I'm hoping to figure out is how to do the same, except on a proper
> >> computer such as the local used ones I'm able to get for less than $200
> >> with 2ghz with 30GB hard disk, 512mb or more ram, etc. So I figure this
> >> should be fine for what I'm planning.
> >>
> >> Example of what I'm trying to do, though based on the low-power embedded
> >> Soekris net4501 system from the TAPR manual's example section:
> >>
> >> http://www.febo.com/time-freq/ntp/soekris/index.html
> >>
> >> ^Aren't those the photos from clock block frequency synthesizer manual?
> >>
> >> Again, I'm wondering if anyone has opinions or experience about doing
> >> such things with NOT an embedded system (as I said, can get a nice 2ghz
> >> or so machine for less than $200 locally at a brick and mortar shop
> >> within walking distance)
> >>
> >> Thanks in advance,
> >> Sarah
> >>
> >>
> >> ___
> >> time-nuts mailing list -- time-nuts@febo.com
> >> To unsubscribe, go to
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> >
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_
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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[bownes]

It all depends on what clock your talking about. Any given PC probably has more 
than one oscillator onboard.
Generally there will be one for the CPU, one for the display circuitry, and 
probably one for the real time clock.

Presuming you are talking about the CPU clock, it should be fairly 
straightforward to find the oscillator package on the motherboard find the pin 
with clock output and feed your clock input there.

On Nov 30, 2012, at 16:59, Bob Camp  wrote:

> Hi
> 
> It's most commonly done with things like a Soekris 45xx series board. You 
> don't need anything very exotic for the frequency conversion. The jitter in 
> the PC is way worse than what the external chips will be creating. 
> 
> The real question is - what is the "magic frequency" on the particular mother 
> board you are going to modify? Once upon a time they all were a pretty 
> predictable 14.xxx MHz. These days, who knows what's going in where…
> 
> Bob
> 
> On Nov 30, 2012, at 4:55 PM, Sarah White  wrote:
> 
>> Has anyone ever used a TAPR clock block or other frequency synthesizer
>> to sort the clock drift / timing problems on a regular computer? I'll
>> probably end up with a used dell or IBM workstation for this purpose.
>> 
>> Recently, I came across a low-cost frequency synthesizer capable of
>> using a 10mhz frequency reference (planning on using the thunderbolt
>> GPSDO I'm working with once I manage to sort out the temperature issues)
>> 
>> http://www.tapr.org/~n8ur/Clock-Block_Manual.pdf
>> 
>> ^ TAPR "Clock Block" has an installation example for how to do what I'm
>> planning with a Soekris net4501 low-cost / low-power embedded device...
>> 
>> What I'm hoping to figure out is how to do the same, except on a proper
>> computer such as the local used ones I'm able to get for less than $200
>> with 2ghz with 30GB hard disk, 512mb or more ram, etc. So I figure this
>> should be fine for what I'm planning.
>> 
>> Example of what I'm trying to do, though based on the low-power embedded
>> Soekris net4501 system from the TAPR manual's example section:
>> 
>> http://www.febo.com/time-freq/ntp/soekris/index.html
>> 
>> ^Aren't those the photos from clock block frequency synthesizer manual?
>> 
>> Again, I'm wondering if anyone has opinions or experience about doing
>> such things with NOT an embedded system (as I said, can get a nice 2ghz
>> or so machine for less than $200 locally at a brick and mortar shop
>> within walking distance)
>> 
>> Thanks in advance,
>> Sarah
>> 
>> 
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> 
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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[shalimr9]

I am not sure that a precision clock will help if the cpu is busy and skips 
clock cycles. I believe this is one of the problems with general purpose OSes 
like Windows.

I believe the better boards like the Soekis use hardware dividers to alleviate 
the cpu busy problem.

Didier

Sent from my Droid Razr 4G LTE wireless tracker.



-Original Message-
From: Sarah White 
To: Discussion of precise time and frequency measurement 
Sent: Fri, 30 Nov 2012 3:55 PM
Subject: [time-nuts] Using a frequency synthesizer replacement for motherboard 
oscillator

Has anyone ever used a TAPR clock block or other frequency synthesizer
to sort the clock drift / timing problems on a regular computer? I'll
probably end up with a used dell or IBM workstation for this purpose.

Recently, I came across a low-cost frequency synthesizer capable of
using a 10mhz frequency reference (planning on using the thunderbolt
GPSDO I'm working with once I manage to sort out the temperature issues)

http://www.tapr.org/~n8ur/Clock-Block_Manual.pdf

^ TAPR "Clock Block" has an installation example for how to do what I'm
planning with a Soekris net4501 low-cost / low-power embedded device...

What I'm hoping to figure out is how to do the same, except on a proper
computer such as the local used ones I'm able to get for less than $200
with 2ghz with 30GB hard disk, 512mb or more ram, etc. So I figure this
should be fine for what I'm planning.

Example of what I'm trying to do, though based on the low-power embedded
Soekris net4501 system from the TAPR manual's example section:

http://www.febo.com/time-freq/ntp/soekris/index.html

^Aren't those the photos from clock block frequency synthesizer manual?

Again, I'm wondering if anyone has opinions or experience about doing
such things with NOT an embedded system (as I said, can get a nice 2ghz
or so machine for less than $200 locally at a brick and mortar shop
within walking distance)

Thanks in advance,
Sarah


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Re: [time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Bob Camp]

Hi

It's most commonly done with things like a Soekris 45xx series board. You don't 
need anything very exotic for the frequency conversion. The jitter in the PC is 
way worse than what the external chips will be creating. 

The real question is - what is the "magic frequency" on the particular mother 
board you are going to modify? Once upon a time they all were a pretty 
predictable 14.xxx MHz. These days, who knows what's going in where…

Bob

On Nov 30, 2012, at 4:55 PM, Sarah White  wrote:

> Has anyone ever used a TAPR clock block or other frequency synthesizer
> to sort the clock drift / timing problems on a regular computer? I'll
> probably end up with a used dell or IBM workstation for this purpose.
> 
> Recently, I came across a low-cost frequency synthesizer capable of
> using a 10mhz frequency reference (planning on using the thunderbolt
> GPSDO I'm working with once I manage to sort out the temperature issues)
> 
> http://www.tapr.org/~n8ur/Clock-Block_Manual.pdf
> 
> ^ TAPR "Clock Block" has an installation example for how to do what I'm
> planning with a Soekris net4501 low-cost / low-power embedded device...
> 
> What I'm hoping to figure out is how to do the same, except on a proper
> computer such as the local used ones I'm able to get for less than $200
> with 2ghz with 30GB hard disk, 512mb or more ram, etc. So I figure this
> should be fine for what I'm planning.
> 
> Example of what I'm trying to do, though based on the low-power embedded
> Soekris net4501 system from the TAPR manual's example section:
> 
> http://www.febo.com/time-freq/ntp/soekris/index.html
> 
> ^Aren't those the photos from clock block frequency synthesizer manual?
> 
> Again, I'm wondering if anyone has opinions or experience about doing
> such things with NOT an embedded system (as I said, can get a nice 2ghz
> or so machine for less than $200 locally at a brick and mortar shop
> within walking distance)
> 
> Thanks in advance,
> Sarah
> 
> 
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[time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

[Sarah White]

Has anyone ever used a TAPR clock block or other frequency synthesizer
to sort the clock drift / timing problems on a regular computer? I'll
probably end up with a used dell or IBM workstation for this purpose.

Recently, I came across a low-cost frequency synthesizer capable of
using a 10mhz frequency reference (planning on using the thunderbolt
GPSDO I'm working with once I manage to sort out the temperature issues)

http://www.tapr.org/~n8ur/Clock-Block_Manual.pdf

^ TAPR "Clock Block" has an installation example for how to do what I'm
planning with a Soekris net4501 low-cost / low-power embedded device...

What I'm hoping to figure out is how to do the same, except on a proper
computer such as the local used ones I'm able to get for less than $200
with 2ghz with 30GB hard disk, 512mb or more ram, etc. So I figure this
should be fine for what I'm planning.

Example of what I'm trying to do, though based on the low-power embedded
Soekris net4501 system from the TAPR manual's example section:

http://www.febo.com/time-freq/ntp/soekris/index.html

^Aren't those the photos from clock block frequency synthesizer manual?

Again, I'm wondering if anyone has opinions or experience about doing
such things with NOT an embedded system (as I said, can get a nice 2ghz
or so machine for less than $200 locally at a brick and mortar shop
within walking distance)

Thanks in advance,
Sarah


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