Re: [time-nuts] PC clock generator without 14.318MHz

[Vladimir Smotlacha]

Chris, I agree with you that additional HW to avoid interrupt latency is 
necessary. My NTP servers  with stable oscillator and HW card processing 
PPS (still in use but some mainboards failed after 10 years of reliable 
service) are described here:

http://archiv.cesnet.cz/doc/techzpravy/2007/ntp-server/

Vladimir

On 10/20/2016 04:38 AM, Chris Albertson wrote:

The last time I read about this it was on an ARM based board.  They clocked
it with a GPSDO.   I think the problem is MUCH easier if you can abandon
the PC platform.

The other story I read solved to problem by adding even more hardware and
some software changes.  They moved the nanosecond counter out of the CPU
chip to a hardware counter and then the PPS signal connected to a latch.
This avoids the interrupt latency.

In most normal NTP servers the interrupt causes the CPU to snapshot its
internal nanosecond counter and store the snapshot in memory and set a flag
so the user space task can then read the value stated in RAM.   This gets
you only microsecond resolution.

With special hardware the counter is latched with external hardware then
then on the interrupt handler only has read the latch and place that valuer
in RAM and set the same flag. The trouble is that EVERY routine that
reads the internal counters has to by modified to read the eternal counter.
As I remember these system ran BSD UNIX.


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Re: [time-nuts] PC clock generator without 14.318MHz

[Chris Albertson]

The last time I read about this it was on an ARM based board.  They clocked
it with a GPSDO.   I think the problem is MUCH easier if you can abandon
the PC platform.

The other story I read solved to problem by adding even more hardware and
some software changes.  They moved the nanosecond counter out of the CPU
chip to a hardware counter and then the PPS signal connected to a latch.
This avoids the interrupt latency.

In most normal NTP servers the interrupt causes the CPU to snapshot its
internal nanosecond counter and store the snapshot in memory and set a flag
so the user space task can then read the value stated in RAM.   This gets
you only microsecond resolution.

With special hardware the counter is latched with external hardware then
then on the interrupt handler only has read the latch and place that valuer
in RAM and set the same flag. The trouble is that EVERY routine that
reads the internal counters has to by modified to read the eternal counter.
   As I remember these system ran BSD UNIX.

On Wed, Oct 19, 2016 at 9:02 AM, Vladimir Smotlacha  wrote:

>
> On 10/18/2016 11:23 PM, Mike Cook wrote:
>
>>
>> Le 18 oct. 2016 à 16:53, Vladimir Smotlacha  a écrit :
>>>
>>>
>>>
>>> Hello,
>>>
>>> I have operated own NTP servers with stable system clock for many years.
>>> The principle is quite simple - I replaced 14.318 MHz quartz with OCXO
>>> based circuit. Now I have to build few more servers with modern mini-ITX
>>> motherboards, however on many of them (e.g. from ASUS) I can’t find any
>>> 14.317 MHz quartz.  Such frequency is a relic of original PC design and I
>>> wonder if it is used any other basic frequency in recent clock generators?
>>>
>>
>> The 14.317MHz xtal was connected to the south bridge controller chip, but
>> for recent CPUs this has gone away as has northbridge and the system clock
>> has been integrated into the PCH (Platform Controller Hub) chip according
>> to Wikipedia, so I suspect that if you find the clock feeding that , then
>> you could stabilize it in that same way.
>>
>>
> Thank you Mike, PCH will be object of my experiments.
> I wonder than probably nobody solved stable clock source in "post 14.318"
> mainboards.
>
> Vladimir
>
>
>>> thanks,
>>> Vladimir
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>> who have not got it. »
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>>
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-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] PC clock generator without 14.318MHz

[Vladimir Smotlacha]

On 10/18/2016 11:23 PM, Mike Cook wrote:



Le 18 oct. 2016 à 16:53, Vladimir Smotlacha  a écrit :



Hello,

I have operated own NTP servers with stable system clock for many years. The 
principle is quite simple - I replaced 14.318 MHz quartz with OCXO based 
circuit. Now I have to build few more servers with modern mini-ITX 
motherboards, however on many of them (e.g. from ASUS) I can’t find any 14.317 
MHz quartz.  Such frequency is a relic of original PC design and I wonder if it 
is used any other basic frequency in recent clock generators?


The 14.317MHz xtal was connected to the south bridge controller chip, but for 
recent CPUs this has gone away as has northbridge and the system clock has been 
integrated into the PCH (Platform Controller Hub) chip according to Wikipedia, 
so I suspect that if you find the clock feeding that , then you could stabilize 
it in that same way.



Thank you Mike, PCH will be object of my experiments.
I wonder than probably nobody solved stable clock source in "post 
14.318" mainboards.


Vladimir



thanks,
Vladimir
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"The power of accurate observation is commonly called cynicism by those who 
have not got it. »
George Bernard Shaw

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Re: [time-nuts] PC clock generator without 14.318MHz

[Hal Murray]

jim...@earthlink.net said:
> What I need is that really boring single camera watching from a single
> viewpoint with a high resolution counter in the field of view.  The "big
> countdown clock" at KSC doesn't show fractions of a second. 

What's the technology for that clock?  I'll guess that was before LEDs so 
they probably used glowing metal.  How long does that take to heat up when a 
segment turns on or cool down when a segment turns off?  Could you recover 
the camera frame offset by carefully examining the intensity in a few frames 
around each second tick?


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] PC clock generator without 14.318MHz

[jimlux]

On 10/18/16 5:06 PM, Tom Van Baak wrote:

Hmm.. there's probably film footage of things with a running counter in
the scene counting tenths or hundredths of a second (sporting events,
nuclear bomb tests, etc.) I wonder if you could see that difference by
single framing something like a filmed 100 meter race where they have an
onscreen timer.

You don't have to go back very far and film cameras used mechanical
governors for speed control.. "quartz lock" is a relatively recent
addition, and as recently as 20 years ago, you had to pay extra for it
when renting camera gear.


Hi Jim,

I recently happened to view the Director's cut of Woodstock. On the bonus disc there's a 
piece called "Synchronization" with amazing information about the extreme 
effort it took to sync 3 days of footage of 12 cameras and 8-track audio tape in an era 
before quartz timing. 60 Hz hum played a role.

Since I know none of you are going to spend 9 hours watching the DVD, I found 
at least one page on the web with part of the story.

Go to https://www.editorsguild.com/V2/magazine/archives/0107/news_article04.htm and skip 
way down Chuck Levey's part, or just text search for the word "sync".

He mentions the wristwatch trick:
   "In 1969, we shot the performance material using AC power in
order to stay in sync. It was clumsy. There were cables. The motors
were heavy and became very hot. In the rain we kept getting shocked.
And don't forget our primitive 'get a shot of your wristwatch'
attempts at time code.


We've all done that...  And an analog watch is easier to read in a fuzzy 
out of focus (too close to the camera) shot than a digital watch.





The last sentence wins a prize:
   "With a laugh, Levey compares the new syncing technologies to those
of the original film. "We were glad when it came to the footage
of The Who, because Pete Townshend's trademark windmill guitar
technique made syncing that passage a little easier," he recalls.



who knew that the who was thinking about time-nuts..


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Re: [time-nuts] PC clock generator without 14.318MHz

[jimlux]

On 10/18/16 4:50 PM, Adrian Godwin wrote:

How about the Apollo launches ?


On Wed, Oct 19, 2016 at 12:40 AM, jimlux  wrote:




What you really want is continuous footage lasting, say, a minute, of some
event (motivating the coverage) where there's an accurate clock visible in
the scene, where the film was originally shot at 24fps, and has been
converted to video.

An interesting quest



But didn't you know, those were all faked in Hollywood

Yes.. the trick is finding a continuous shot.. I did some googling and 
didn't turn up a continuous shot.. lots of "edited highlights" reels..


What I need is that really boring single camera watching from a single 
viewpoint with a high resolution counter in the field of view.  The "big 
countdown clock" at KSC doesn't show fractions of a second.


I also found some stuff from the 1976 olympics (200m and 400m), but it's 
multiple camera angles and obviously video recording.



It will likely be something that was shot for "scientific purposes" (so 
the clock's in the scene) that someone has telecine'd for amusement  - 
I've got a DVD full of atomic bomb detonation clips at home.. maybe one 
of those, because they just took the archival footage and put it on DVD, 
no edits, no color correction, etc.



There might also be some sort of newsreel footage of some piece of 
appropriate equipment (e.g. high speed counter) is featured for a few 
seconds.. if someone had one of those older scalers with the 10 neon 
bulbs for each digit arranged in columns, that might work.. if they're 
counting milliseconds or microseconds, then a few second clip would be 
long enough. Or a counter with a fast discrete display (like an older HP 
with a non-multiplexed display)



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Re: [time-nuts] PC clock generator without 14.318MHz

[Magnus Danielson]

Attila,

On 10/19/2016 01:25 AM, Attila Kinali wrote:

On Tue, 18 Oct 2016 23:36:55 +0200
Magnus Danielson  wrote:


To this day, the 1.001 factor haunts us in all modern hardware and
timing designs, including the latest synchronization standards.

It's fascinating that we have been simulating several centuries into the
future to ensure that the algorithms for the synchronization will make
the 1.001 factor keep working as intended. I wrote one such simulator
being used.


So, you are doing the inverse of a programmer archeologist[1]?

SCNR :-)

On a more more serious note: what exactly have you been simulating?
And how does this frequency make a difference?


When you use GPS/GNSS as source for your TV-signals, you define a 
suitable epoch, such as the PTP Epoch. At the Epoch, all sample values 
where in phase, and from then on they progress with SI-second, so with a 
TAI-approximation you can calculate it. The time of day, date etc. you 
derive from the UTC-approximation.


The 1.001 factor then requires a 1001 s long cycle before it aligns up.
Considering some other factors, this can be as long as 4004 s for 
everything to aline up. So, TAI-time modulus 4004 s and from there it is 
relatively simple for all the phases.


You would find the details in SMPTE 2059-1 and SMPTE 2059-2.

All the traditional formats can be expressed in this time. In order to 
achieve it fully, the PTP server needs to extend with additional info, 
which among other things tells us how the TV station is setup and when 
the common daily jamming occurs.


Now, as we do full-HD signal, it is 2,97 Gb/s for European TV or 
2,97/1,001 Gb/s for US TV. So we naturally need a way to get these 
values in low-jitter form, which is a bit interesting. The older BT.656 
SDI format, also known as SMPTE 259 had a nice and round common number 
of 270 Mb/s for both formats, but somebody didn't think it through for 
the HDTV variant and the number-magic broke up.


We keep inherit this into 4k video and 8k I guess.

Lovely, isn't it?

Cheers,
Magnus
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Re: [time-nuts] PC clock generator without 14.318MHz

[Tom Van Baak]

> Hmm.. there's probably film footage of things with a running counter in 
> the scene counting tenths or hundredths of a second (sporting events, 
> nuclear bomb tests, etc.) I wonder if you could see that difference by 
> single framing something like a filmed 100 meter race where they have an 
> onscreen timer.
> 
> You don't have to go back very far and film cameras used mechanical 
> governors for speed control.. "quartz lock" is a relatively recent 
> addition, and as recently as 20 years ago, you had to pay extra for it 
> when renting camera gear.

Hi Jim,

I recently happened to view the Director's cut of Woodstock. On the bonus disc 
there's a piece called "Synchronization" with amazing information about the 
extreme effort it took to sync 3 days of footage of 12 cameras and 8-track 
audio tape in an era before quartz timing. 60 Hz hum played a role.

Since I know none of you are going to spend 9 hours watching the DVD, I found 
at least one page on the web with part of the story.

Go to https://www.editorsguild.com/V2/magazine/archives/0107/news_article04.htm 
and skip way down Chuck Levey's part, or just text search for the word "sync".

He mentions the wristwatch trick:
   "In 1969, we shot the performance material using AC power in
order to stay in sync. It was clumsy. There were cables. The motors
were heavy and became very hot. In the rain we kept getting shocked.
And don't forget our primitive 'get a shot of your wristwatch'
attempts at time code.

The last sentence wins a prize:
   "With a laugh, Levey compares the new syncing technologies to those
of the original film. "We were glad when it came to the footage
of The Who, because Pete Townshend's trademark windmill guitar
technique made syncing that passage a little easier," he recalls.

/tvb

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Re: [time-nuts] PC clock generator without 14.318MHz

[Adrian Godwin]

How about the Apollo launches ?


On Wed, Oct 19, 2016 at 12:40 AM, jimlux  wrote:

> On 10/18/16 4:25 PM, Magnus Danielson wrote:
>
>> Jim,
>>
>> On 10/19/2016 12:51 AM, jimlux wrote:
>>
>>> On 10/18/16 2:30 PM, Tom Van Baak wrote:
>>>
 Hi Vladimir,

 Some of these numbers survive to the present. I'm typing this post on
 an XP laptop where QueryPerformanceCounter() has a Frequency.QuadPart
 of, you guessed it, 3579545 Hz, which is why my Win32 laptop's
 high-res clock has ~279 ns resolution.

 For more fun with time, frequency, oscillators, and prime numbers,
 see: http://www.poynton.com/PDFs/Magic_Numbers.pdf


>>> and this is why clocks in film movies on TV run slightly slow..
>>> because the film was shot at 24 fps, and it's converted to 29.97 frame
>>> rate (in the US) by a 3:2 pulldown scheme.
>>>
>>> I am sure that all the time nuts here notice that 0.1% rate difference.
>>> Over a half hour TV program it adds up to almost 2 seconds of offset.
>>> (that's just because we watch things like movies shot of counters
>>> running).
>>>
>>> Hmm.. there's probably film footage of things with a running counter in
>>> the scene counting tenths or hundredths of a second (sporting events,
>>> nuclear bomb tests, etc.) I wonder if you could see that difference by
>>> single framing something like a filmed 100 meter race where they have an
>>> onscreen timer.
>>>
>>
>> The time-code of TV and film production runs with a frame-counter.
>> Now, since the 30/1.001 factor is uneven, to get things into shape the
>> factor is compensated using the drop-frame method.
>>
>
> SO that compensates in the "big sense" so that "timecode" and "wall clock"
> line up..
>
> But when they do the original telecine, they're basically running a 30fps
> (interpolated from 24 fps) sequence of frames at 29.97.  Over the air,
> there will usually be a commercial break and they can add/drop any
> arbitrary number of frames to get it to line up (should they even care
> about whether the on-screen clock ticking the seconds actually lines up)
>
> So I was thinking about something where you get a broadcast (or maybe a
> video conversion on DVD/tape/online) that is a continuous piece of film.
>
> Seems that something like 100 meter race, which lasts 10 seconds, and will
> have an on screen timer to hundredths isn't quite long enough to see the
> 1.001 error (and would it be one continuous shot, or would they have edited
> film together from different viewpoints).
>
> What about a filmed rocket launch with a countdown timer or similar? they
> might have one continuous piece of film long enough.
>
> Partly, its going to be limited by the magazine size of the camera: a 400
> ft magazine is a bit more than 6 minutes (1 ft = 1 second in rough terms),
> so that's plenty long to see the difference.
>
> What you really want is continuous footage lasting, say, a minute, of some
> event (motivating the coverage) where there's an accurate clock visible in
> the scene, where the film was originally shot at 24fps, and has been
> converted to video.
>
> An interesting quest
>
>
>
>
>
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Re: [time-nuts] PC clock generator without 14.318MHz

[jimlux]

On 10/18/16 4:25 PM, Magnus Danielson wrote:

Jim,

On 10/19/2016 12:51 AM, jimlux wrote:

On 10/18/16 2:30 PM, Tom Van Baak wrote:

Hi Vladimir,

Some of these numbers survive to the present. I'm typing this post on
an XP laptop where QueryPerformanceCounter() has a Frequency.QuadPart
of, you guessed it, 3579545 Hz, which is why my Win32 laptop's
high-res clock has ~279 ns resolution.

For more fun with time, frequency, oscillators, and prime numbers,
see: http://www.poynton.com/PDFs/Magic_Numbers.pdf



and this is why clocks in film movies on TV run slightly slow..
because the film was shot at 24 fps, and it's converted to 29.97 frame
rate (in the US) by a 3:2 pulldown scheme.

I am sure that all the time nuts here notice that 0.1% rate difference.
Over a half hour TV program it adds up to almost 2 seconds of offset.
(that's just because we watch things like movies shot of counters
running).

Hmm.. there's probably film footage of things with a running counter in
the scene counting tenths or hundredths of a second (sporting events,
nuclear bomb tests, etc.) I wonder if you could see that difference by
single framing something like a filmed 100 meter race where they have an
onscreen timer.


The time-code of TV and film production runs with a frame-counter.
Now, since the 30/1.001 factor is uneven, to get things into shape the
factor is compensated using the drop-frame method.


SO that compensates in the "big sense" so that "timecode" and "wall 
clock" line up..


But when they do the original telecine, they're basically running a 
30fps (interpolated from 24 fps) sequence of frames at 29.97.  Over the 
air, there will usually be a commercial break and they can add/drop any 
arbitrary number of frames to get it to line up (should they even care 
about whether the on-screen clock ticking the seconds actually lines up)


So I was thinking about something where you get a broadcast (or maybe a 
video conversion on DVD/tape/online) that is a continuous piece of film.


Seems that something like 100 meter race, which lasts 10 seconds, and 
will have an on screen timer to hundredths isn't quite long enough to 
see the 1.001 error (and would it be one continuous shot, or would they 
have edited film together from different viewpoints).


What about a filmed rocket launch with a countdown timer or similar? 
they might have one continuous piece of film long enough.


Partly, its going to be limited by the magazine size of the camera: a 
400 ft magazine is a bit more than 6 minutes (1 ft = 1 second in rough 
terms), so that's plenty long to see the difference.


What you really want is continuous footage lasting, say, a minute, of 
some event (motivating the coverage) where there's an accurate clock 
visible in the scene, where the film was originally shot at 24fps, and 
has been converted to video.


An interesting quest




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Re: [time-nuts] PC clock generator without 14.318MHz

[Attila Kinali]

On Tue, 18 Oct 2016 23:36:55 +0200
Magnus Danielson  wrote:

> To this day, the 1.001 factor haunts us in all modern hardware and 
> timing designs, including the latest synchronization standards.
> 
> It's fascinating that we have been simulating several centuries into the 
> future to ensure that the algorithms for the synchronization will make 
> the 1.001 factor keep working as intended. I wrote one such simulator 
> being used.

So, you are doing the inverse of a programmer archeologist[1]? 

SCNR :-)

On a more more serious note: what exactly have you been simulating?
And how does this frequency make a difference?

Attila Kinali


[1] http://lambda-the-ultimate.org/node/4424
-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] PC clock generator without 14.318MHz

[Magnus Danielson]

Jim,

On 10/19/2016 12:51 AM, jimlux wrote:

On 10/18/16 2:30 PM, Tom Van Baak wrote:

Hi Vladimir,

Some of these numbers survive to the present. I'm typing this post on
an XP laptop where QueryPerformanceCounter() has a Frequency.QuadPart
of, you guessed it, 3579545 Hz, which is why my Win32 laptop's
high-res clock has ~279 ns resolution.

For more fun with time, frequency, oscillators, and prime numbers,
see: http://www.poynton.com/PDFs/Magic_Numbers.pdf



and this is why clocks in film movies on TV run slightly slow..
because the film was shot at 24 fps, and it's converted to 29.97 frame
rate (in the US) by a 3:2 pulldown scheme.

I am sure that all the time nuts here notice that 0.1% rate difference.
Over a half hour TV program it adds up to almost 2 seconds of offset.
(that's just because we watch things like movies shot of counters running).

Hmm.. there's probably film footage of things with a running counter in
the scene counting tenths or hundredths of a second (sporting events,
nuclear bomb tests, etc.) I wonder if you could see that difference by
single framing something like a filmed 100 meter race where they have an
onscreen timer.


The time-code of TV and film production runs with a frame-counter.
Now, since the 30/1.001 factor is uneven, to get things into shape the 
factor is compensated using the drop-frame method. The sad thing is that 
when you do the math, the drop-frame method only partially compensate 
the 1.001 factor, so over a day you still drift, albeit slower. So, for 
a TV-station setup, you throw a wrench into the clock machinery in order 
to jam the gears into time again. Now, when you do that, all the 
decoding stuff can "jump" in unexpected way, so you try to schedule it 
for when you are off air or not transmitting anything important. Oh, and 
we have to inherit all this into the new stuff too.


Interesting when you have to explain to them that leap seconds is 
introduced at the same time, regardless of local time-scale. So, 
leap-seconds would also have to be jammed-in.


Cheers,
Magnus
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Re: [time-nuts] PC clock generator without 14.318MHz

[jimlux]

On 10/18/16 2:30 PM, Tom Van Baak wrote:

Hi Vladimir,

Some of these numbers survive to the present. I'm typing this post on
an XP laptop where QueryPerformanceCounter() has a Frequency.QuadPart
of, you guessed it, 3579545 Hz, which is why my Win32 laptop's
high-res clock has ~279 ns resolution.

For more fun with time, frequency, oscillators, and prime numbers,
see: http://www.poynton.com/PDFs/Magic_Numbers.pdf



and this is why clocks in film movies on TV run slightly slow.. 
because the film was shot at 24 fps, and it's converted to 29.97 frame 
rate (in the US) by a 3:2 pulldown scheme.


I am sure that all the time nuts here notice that 0.1% rate difference. 
Over a half hour TV program it adds up to almost 2 seconds of offset. 
(that's just because we watch things like movies shot of counters running).


Hmm.. there's probably film footage of things with a running counter in 
the scene counting tenths or hundredths of a second (sporting events, 
nuclear bomb tests, etc.) I wonder if you could see that difference by 
single framing something like a filmed 100 meter race where they have an 
onscreen timer.


You don't have to go back very far and film cameras used mechanical 
governors for speed control.. "quartz lock" is a relatively recent 
addition, and as recently as 20 years ago, you had to pay extra for it 
when renting camera gear.


When I was in that business, one of the things I used to do was modify 
PCs so that they could be locked together - the frequency tolerance on 
PCs is pretty bad, so if you have a set with a bunch of PCs they could 
adjust the camera shutter phase and frame rate so you didn't get the 
sync bars on one screen, but not on all, and furthermore, over a long 
take, they would drift relative to each other, so even if you had them 
all lined up to start...


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Re: [time-nuts] PC clock generator without 14.318MHz

[Magnus Danielson]

Poul-Henning,

On 10/18/2016 10:38 PM, Poul-Henning Kamp wrote:


In message , Gary Woods writes:

On Tue, 18 Oct 2016 16:53:15 +0200, you wrote:


14.317 MHz quartz.  Such frequency is a relic of original PC design


It's 4X the color subcarrier frequency in NTSC (originally U.S.)
television; rapidly becoming a dinosaur. I'm sure it was used in computers
to make color video easier. Newer boards doubtless use much faster clocks
and synthesize what the parts need.


It's 14.3181818 MHz and it has a most facinating history - if you care
for that sort of thing:


https://en.wikipedia.org/wiki/Colorburst#Rationale_for_NTSC_Color_burst_frequency


To this day, the 1.001 factor haunts us in all modern hardware and 
timing designs, including the latest synchronization standards.


It's fascinating that we have been simulating several centuries into the 
future to ensure that the algorithms for the synchronization will make 
the 1.001 factor keep working as intended. I wrote one such simulator 
being used.


Cheers,
Magnus
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Re: [time-nuts] PC clock generator without 14.318MHz

[Tom Van Baak]

Hi Vladimir,

1) Maybe you can use a DDS chip to create your 14.328 MHz signal, or

2) Do it yourself using a PLL at 45.454 kHz using 220 and 315 dividers:

10.00 MHz / 220 = 45454.545 Hz
14.318181 MHz / 315 = 45454.545 Hz

This works because your 14.31818 MHz number is defined as 4x the 3.579545 MHz 
NTSC colorburst frequency,
which is defined precisely as 60 * 1000/1001 * 525/2 * 455/2,
which expands to (60 * 1000 * 3*5*5*7 * 5*7*13) / (7*11*13 * 2 * 2),
which reduces to 315 / 88 MHz.
So that's why 10.00 MHz * 315 / 220 = 14.318181 MHz, exactly.

Note also that:
 -  14.31818 MHz / 3 = 4.77273 MHz, the CPU clock rate for the original IBM PC
 -  14.31818 MHz / 4 = 3.579545 MHz, the colorburst frequency (for PC video)
 -  14.31818 MHz / 12 = 1.193182 MHz, the Intel 8253 timer clock (the 
historical root of all PC timekeeping)

Some of these numbers survive to the present. I'm typing this post on an XP 
laptop where QueryPerformanceCounter() has a Frequency.QuadPart of, you guessed 
it, 3579545 Hz, which is why my Win32 laptop's high-res clock has ~279 ns 
resolution.

For more fun with time, frequency, oscillators, and prime numbers, see:
http://www.poynton.com/PDFs/Magic_Numbers.pdf

/tvb

- Original Message - 
From: "Vladimir Smotlacha" <v...@cesnet.cz>
To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com>
Sent: Tuesday, October 18, 2016 7:53 AM
Subject: [time-nuts] PC clock generator without 14.318MHz




Hello,

I have operated own NTP servers with stable system clock for many years. 
The principle is quite simple - I replaced 14.318 MHz quartz with OCXO 
based circuit. Now I have to build few more servers with modern mini-ITX 
motherboards, however on many of them (e.g. from ASUS) I can’t find any 
14.317 MHz quartz.  Such frequency is a relic of original PC design and 
I wonder if it is used any other basic frequency in recent clock generators?

thanks,
Vladimir

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Re: [time-nuts] PC clock generator without 14.318MHz

[Mike Cook]

> Le 18 oct. 2016 à 16:53, Vladimir Smotlacha  a écrit :
> 
> 
> 
> Hello,
> 
> I have operated own NTP servers with stable system clock for many years. The 
> principle is quite simple - I replaced 14.318 MHz quartz with OCXO based 
> circuit. Now I have to build few more servers with modern mini-ITX 
> motherboards, however on many of them (e.g. from ASUS) I can’t find any 
> 14.317 MHz quartz.  Such frequency is a relic of original PC design and I 
> wonder if it is used any other basic frequency in recent clock generators?

The 14.317MHz xtal was connected to the south bridge controller chip, but for 
recent CPUs this has gone away as has northbridge and the system clock has been 
integrated into the PCH (Platform Controller Hub) chip according to Wikipedia, 
so I suspect that if you find the clock feeding that , then you could stabilize 
it in that same way.  

> 
> thanks,
>   Vladimir
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"The power of accurate observation is commonly called cynicism by those who 
have not got it. »
George Bernard Shaw

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Re: [time-nuts] PC clock generator without 14.318MHz

[Poul-Henning Kamp]

In message , Gary Woods writes:
>On Tue, 18 Oct 2016 16:53:15 +0200, you wrote:
>
>>14.317 MHz quartz.  Such frequency is a relic of original PC design
>
>It's 4X the color subcarrier frequency in NTSC (originally U.S.)
>television; rapidly becoming a dinosaur. I'm sure it was used in computers
>to make color video easier. Newer boards doubtless use much faster clocks
>and synthesize what the parts need.

It's 14.3181818 MHz and it has a most facinating history - if you care
for that sort of thing:


https://en.wikipedia.org/wiki/Colorburst#Rationale_for_NTSC_Color_burst_frequency


-- 
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] PC clock generator without 14.318MHz

[Gary Woods]

On Tue, 18 Oct 2016 16:53:15 +0200, you wrote:

>14.317 MHz quartz.  Such frequency is a relic of original PC design

It's 4X the color subcarrier frequency in NTSC (originally U.S.)
television; rapidly becoming a dinosaur. I'm sure it was used in computers
to make color video easier. Newer boards doubtless use much faster clocks
and synthesize what the parts need.
]'

-- 
Gary Woods AKA K2AHC- PGP key on request, or at home.earthlink.net/~garygarlic
Zone 5/4 in upstate New York, 1420' elevation. NY WO G
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[time-nuts] PC clock generator without 14.318MHz

[Vladimir Smotlacha]

Hello,

I have operated own NTP servers with stable system clock for many years. 
The principle is quite simple - I replaced 14.318 MHz quartz with OCXO 
based circuit. Now I have to build few more servers with modern mini-ITX 
motherboards, however on many of them (e.g. from ASUS) I can’t find any 
14.317 MHz quartz.  Such frequency is a relic of original PC design and 
I wonder if it is used any other basic frequency in recent clock generators?


thanks,
Vladimir
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