Re: Scrounging - was Floating point routines for the 6809

[Peter Coghlan via cctalk]

>
> Or the time an English co-worker related the story surrounding her
> initial job interval in the US.  She described the stunned look on the
> face of the desk clerk at the local Holiday Inn when she asked to be
> knocked up at 7:30 the next morning.
>

This reminds me of the rather surprised look on my Australian colleague's
face when I said I was going to have a root in the cupboard for a missing
manual.

Regards,
Peter Coghlan

Re: Cross-talk square-wave?

[Chuck Guzis via cctalk]

I'll offer a suggestion that if your SD card *must* be a significant
distance from its host, that you employ a small MCU at the SD card and
use a more noise-immune protocol to transmit data to the host.

Small MCUs today are very  inexpensive.

--Chuck

Re: Cross-talk square-wave?

[dwight via cctalk]

again, I don't know the circuit, but I have personally witnessed this behavior 
on my PDP-8/e where a 7474 flip flop chip was bad. The input looked great and 
the output was "half baked"


I'll bet that flop was a Fairchild.

Dwight



From: cctalk  on behalf of W2HX via cctalk 

Sent: Wednesday, March 29, 2017 6:48:09 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: RE: Cross-talk square-wave?

I am still not convinced it is coupling at all. You would expect the affected 
line to show a signal like dV/dt , no? I just don't think you can get square 
waves from square waves. That's not to say the input of some logic somewhere 
isn't getting triggered by unintended coupling and then getting "squared up" in 
some gate to produce the square we see.

Oh, and 270K surely is a transmission line load if the source has a 
characteristic impedance of 270K. Granted, that seems unusual and I don't know 
what the circuit looks like, but yes, most probably it is not a matched load. 
Having said that, given such a probable mismatch, then it is even harder to 
believe one could successfully couple a square wave onto such a transmission 
line unless the signal is actually being asserted on the line at a low 
impedance (ie the intentional output of a gate somewhere).

Looking at this picture
http://pdp10.froghouse.org/qsic/pic_24_1.gif

this shows exactly what I would expect to see with cross talk the little 
glitches on the CS line that correspond to edges on the clock signal. Classic 
dV/dt. scenario.

Looking at this one
http://pdp10.froghouse.org/qsic/pic_24_2.gif

again, I don't know the circuit, but I have personally witnessed this behavior 
on my PDP-8/e where a 7474 flip flop chip was bad. The input looked great and 
the output was "half baked"
Here is a screenshot of what I was seeing (look for "Line OUT E29 pin5" on the 
scope screenshot...)
http://w2hx.com/x/VintageComp/PDP-8e/M8650/LecroyScreen14.png
(post on that subject is here:  
http://www.vcfed.org/forum/showthread.php?55171-PDP-8-e-Project/page6 )

Anyhow, I dunno. My jury is still out on this one.

Eugene


-Original Message-
From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of dwight via 
cctalk
Sent: Wednesday, March 29, 2017 8:33 PM
To: Al Kossow; General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Cross-talk square-wave?

270K is not a transmission line load.

As I recall ribbon cable is around 100-150 ohms

impedance some place.

The signal does look nice and square.

I doubt is is inductive coupling, with that high a

load, I'd say it was capacitive.

inductive coupling requires current flowing.

Dwight



From: cctalk  on behalf of Al Kossow via cctalk 

Sent: Wednesday, March 29, 2017 2:35:54 PM
To: cctalk@classiccmp.org
Subject: Re: Cross-talk square-wave?



On 3/29/17 2:14 PM, David Bridgham via cctalk wrote:
> And I think this picture is the smoking gun.
>
> http://pdp10.froghouse.org/qsic/pic_24_2.gif
>
> Again, the bottom trace is the CS signal in question and the upper
> trace is now one of the QBUS DAL lines (after the bus transceiver and
> level
> converter) that's running across the ribbon cable near the CS signal.
> It does appear that induction can make a fairly clean square wave.
>
>

simple thing to try is split the ribbon cable between the two signals

Re: Scrounging - was Floating point routines for the 6809

[Guy Dawson via cctalk]

That time in an open lab at IBM Austin when a newly arrived fellow Brit
announced that he had to go out and have a fag.

On 30 March 2017 at 13:18, Peter Coghlan via cctalk 
wrote:

> >
> > Or the time an English co-worker related the story surrounding her
> > initial job interval in the US.  She described the stunned look on the
> > face of the desk clerk at the local Holiday Inn when she asked to be
> > knocked up at 7:30 the next morning.
> >
>
> This reminds me of the rather surprised look on my Australian colleague's
> face when I said I was going to have a root in the cupboard for a missing
> manual.
>
> Regards,
> Peter Coghlan
>
>


-- 
4.4 > 5.4

Wyse keyboards and their variants

[Electronics Plus via cctalk]

Wyse, Link, etc.

Does anyone still use these on actual terminals?

I have some guys coming to scrounge on Saturday, and they want them for is
to desolder the switches.

If you need some for actual use, please let me know the exact model you want
so it does not get parted out.

 

Cindy Croxton

Electronics Plus

 

Re: Cross-talk square-wave?

[Noel Chiappa via cctalk]

> From: Allison

> FYI this is the same problem designers hit with DRAMS back 40 years ago.

This didn't ring (pun not intended) a bell for me; can you say a bit more?

> From: Chuck Guzis

> I'll offer a suggestion that if your SD card *must* be a significant
> distance from its host

Like I said, this is a pre-prototype; on the production units, there will be
_no_ cable. The SD socket will be about 1-2" from the FPGA.

> From: Dwight Kelvey

> this behavior on my PDP-8/e where a 7474 flip flop chip was bad. The
> input looked great and the output was "half baked"

There's no chip at all on the driving end of the line (just that 470K
resistor); we see this with the SD card _unplugged_. And we see the exact
same thing on several lines.


I'm still not clear, from the discussion, how exactly that nice 'square-wave'
interference is happening - could it be capacitative crosstalk? (I'd have
thought capacitative cross-talk would be inverted - driving a positive voltage
on one 'side' of the 'capacitor' would, I would think, induce an oppposing
voltage on the other. But I'm clearly no EE! :-)

Noel

Re: Cross-talk square-wave?

[ben via cctalk]

On 3/30/2017 11:22 AM, Chuck Guzis via cctalk wrote:

I'll offer a suggestion that if your SD card *must* be a significant
distance from its host, that you employ a small MCU at the SD card and
use a more noise-immune protocol to transmit data to the host.

Small MCUs today are very  inexpensive.


GO ANALOG ... ONLY A LITLE BIT OF A PROBLEM. :)


--Chuck


Well that does not solve the ring, but off loading
the SD card is a good idea, if you have the software
time for a new cpu. Most of the time upper managment
drags thier feet, unless they want it yesterday.
Ben.

Anyone want a Sun T-shirt?

[Chuck Guzis via cctalk]

It's what, 27 years old...

Trying to de-junk my clothes closet, I ran across an XL t-shirt bearing,
on the front, a image of a ladybug with a red circle and bar across is
and the legend "Getting out the last bugs".  On the back, it has the Sun
logo and "SunStruck  4.1.89 (Wanda)".

It's in decent condition and probably dates from the time my wife worked
at Sun, even though she had nothing to do with the project in question.

Anyone want it?  Pay for first-class mail (I'll stuff it into an
envelope) and it's yours.  Otherwise, it goes to Goodwill.

--Chuck

Re: Cross-talk square-wave?

[Chuck Guzis via cctalk]

On 03/30/2017 01:21 PM, ben via cctalk wrote:

> Well that does not solve the ring, but off loading the SD card is a
> good idea, if you have the software time for a new cpu. Most of the
> time upper managment drags thier feet, unless they want it
> yesterday. Ben.

Well, Noel has stated that this will not be the situation in the final
stage, but my suggestion was done in the spirit of having a well-behaved
low-impedance linkup with the host; not something that resembles an antenna.

--Chuck

Trip to CHM - Hotel/Restaurant Advice

[Rick Bensene via cctalk]

Hello, all,

In mid-June, I am planning a trip to Mountain View for two days to visit the 
Computer History Museum.

I plan on flying out of Portland early AM on June 14, checking into hotel, then 
heading straight to the museum for the day.
I will go back to the hotel for the evening, and return to the museum on the 
15th, and stay into early afternoon, and then check out of the hotel and head 
to the airport to return home.

I haven't been to CHM before, and am looking forward to spending an extended 
period of time there.

What I'm asking for is help/recommendations in terms of a good hotel to stay at 
that is relatively close to the museum.  I don't want to be in a luxury hotel, 
nor do I want to be in a dive.
I'd also like to be in a place that has a restaurant relatively close by 
(preferably within walking distance) that I could get some decent meals 
(breakfast/dinner) while I'm there.

Unless this is a topic of general interest to the group, it'd probably be best 
to reply to me directly rather than post responses to the list.

Many thanks,
-Rick
--
Rick Bensene
The Old Calculator Museum
http://oldcalculatormuseum.com

Re: Cross-talk square-wave?

[dwight via cctalk]

I didn't look clearly at the trace but it could also be

a reflected un-terminated line and not cross talk.

Dwight



From: cctalk  on behalf of Chuck Guzis via 
cctalk 
Sent: Thursday, March 30, 2017 1:59:00 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Cross-talk square-wave?

On 03/30/2017 01:21 PM, ben via cctalk wrote:

> Well that does not solve the ring, but off loading the SD card is a
> good idea, if you have the software time for a new cpu. Most of the
> time upper managment drags thier feet, unless they want it
> yesterday. Ben.

Well, Noel has stated that this will not be the situation in the final
stage, but my suggestion was done in the spirit of having a well-behaved
low-impedance linkup with the host; not something that resembles an antenna.

--Chuck

Re: Cross-talk square-wave?

[Brent Hilpert via cctalk]

On 2017-Mar-30, at 1:13 PM, Noel Chiappa via cctalk wrote:
>> From: Allison
> 
>> FYI this is the same problem designers hit with DRAMS back 40 years ago.
> 
> This didn't ring (pun not intended) a bell for me; can you say a bit more?
> 
>> From: Chuck Guzis
> 
>> I'll offer a suggestion that if your SD card *must* be a significant
>> distance from its host
> 
> Like I said, this is a pre-prototype; on the production units, there will be
> _no_ cable. The SD socket will be about 1-2" from the FPGA.
> 
>> From: Dwight Kelvey
> 
>> this behavior on my PDP-8/e where a 7474 flip flop chip was bad. The
>> input looked great and the output was "half baked"
> 
> There's no chip at all on the driving end of the line (just that 470K
> resistor); we see this with the SD card _unplugged_. And we see the exact
> same thing on several lines.
> 
> 
> I'm still not clear, from the discussion, how exactly that nice 'square-wave'
> interference is happening - could it be capacitative crosstalk? (I'd have
> thought capacitative cross-talk would be inverted - driving a positive voltage
> on one 'side' of the 'capacitor' would, I would think, induce an oppposing
> voltage on the other. But I'm clearly no EE! :-)

I don't have a full enough picture of the circuit and circumstances to provide 
a definitive suggestion but, some principles:

Yes, you can 'pass' a square wave through a capacitor - if you couldn't then 
all the theory behind capacitor-coupled audio amplifiers would be shot.
The condition required to do so is a long resistor - capacitor time constant 
relative to the period of the (square) wave:
RC time constant:  t(seconds) = R (ohms) * C (farads)

With a high load R, and large enough C, the current in an R-C series circuit is 
limited to a tiny level, so it takes a long time for the cap to fully charge.
For as long as the cap is charging there is current flowing through the R and 
so you see a voltage drop across the R.
If you reduce the R value or the C value, at some point you would see the 
square wave start to distort (the flat top would start to slope down to the 
right / later in time),
as the capacitor would start to reach full charge within the period of the 
square wave and the voltage would start to divide between the C and R.

No, you won't see the inverse polarity, if you drive a + voltage to one side of 
the cap it sucks the electrons out of the plate on that side, that attracts 
electrons into the other 'load-side' plate. Those electrons are coming from 
(being drawn away from) the rest of the load side circuit, here through the R, 
so you see a + voltage across the R (current is flowing from GND through R into 
the C, so the RC-junction side of R is more + than the GND side of the R).

Your circuit:

It's not clear C-coupling is what's going on here (the wave shape looks pretty 
sharp for what I understand of the circuit/layout).
Notably though, C-coupling would remove any DC bias, but David's screen shot 
indicates a DC bias on the line.

Is this line currently connected to the FPGA, or is it just the wire and R?
Perhaps the bias is coming from the FPGA, with C-coupling of the wave via the 
wire.
Or perhaps it's all crosstalk from within the FPGA, 'visible' because of the 
high load R.

If the wire and FPGA pin are connected, separate them (reduce the wire circuit 
to just the wire and R to GND): see whether the DC bias and/or the square wave 
disappear.

You could play with reducing the load R value to see what happens to the sig 
level and wave shape.

(You've mentioned both 470K and 270K for the R, could make a difference to the 
analysis).

Re: Trip to CHM - Hotel/Restaurant Advice

[Cory Heisterkamp via cctalk]

On Mar 30, 2017, at 4:17 PM, Rick Bensene via cctalk wrote:

> Hello, all,
> 
> In mid-June, I am planning a trip to Mountain View for two days to visit the 
> Computer History Museum.
> 
> I plan on flying out of Portland early AM on June 14, checking into hotel, 
> then heading straight to the museum for the day.
> I will go back to the hotel for the evening, and return to the museum on the 
> 15th, and stay into early afternoon, and then check out of the hotel and head 
> to the airport to return home.
> 
> I haven't been to CHM before, and am looking forward to spending an extended 
> period of time there.
> 
> What I'm asking for is help/recommendations in terms of a good hotel to stay 
> at that is relatively close to the museum.  I don't want to be in a luxury 
> hotel, nor do I want to be in a dive.
> I'd also like to be in a place that has a restaurant relatively close by 
> (preferably within walking distance) that I could get some decent meals 
> (breakfast/dinner) while I'm there.
> 
> Unless this is a topic of general interest to the group, it'd probably be 
> best to reply to me directly rather than post responses to the list.
> 
> Many thanks,
> -Rick
> --
> Rick Bensene
> The Old Calculator Museum
> http://oldcalculatormuseum.com
> 


I'd also be interested in any recommendations, so might as well list-post, 
it'll be of value to a couple of us. 

Last I was there was this time of year in 2014 and I really should get back 
(spent the entire day there and never saw it all). Having IHG points to use, I 
found a Holiday Inn Express in Belmont that didn't charge an arm and a leg (14 
miles from CHM) that was clean and comfortable and I found it an easy walk to 
several restaurants. One bit of advice, some of the live exhibits, like the 
1401 demo, only run on certain days, so check the CHM calendar in advance if 
there's something you absolutely want to see live. -Cory

Re: Anyone want a Sun T-shirt?

[Mark Linimon via cctalk]

If no one who e.g. worked for Sun steps up, I'll take it.

mcl

Re: Trip to CHM - Hotel/Restaurant Advice

[Tony Aiuto via cctalk]

You want the Hampton Inn.
https://www.google.com/maps/place/Hampton+Inn+%26+Suites+Mountain+View/@37.3950988,-122.0791475,15.53z/data=!4m8!1m2!2m1!1shotels+near+Mountain+View,+CA!3m4!1s0x0:0xc7d978e934c5a2ca!8m2!3d37.3988499!4d-122.0754889

It is walking distance to the light rail station and Castro street.
Mountain View is pretty much a cultural wasteland. If you don't have a car,
the only walkable places to eat are off Castro. You could even walk to the
CHM - it might even be quicker than car given MTV traffic.
The rail from SF airport is surprisingly slow. San Jose may be a better
choice.


On Thu, Mar 30, 2017 at 6:19 PM, Cory Heisterkamp via cctalk <
cctalk@classiccmp.org> wrote:

>
>
> On Mar 30, 2017, at 4:17 PM, Rick Bensene via cctalk wrote:
>
> > Hello, all,
> >
> > In mid-June, I am planning a trip to Mountain View for two days to visit
> the Computer History Museum.
> >
> > I plan on flying out of Portland early AM on June 14, checking into
> hotel, then heading straight to the museum for the day.
> > I will go back to the hotel for the evening, and return to the museum on
> the 15th, and stay into early afternoon, and then check out of the hotel
> and head to the airport to return home.
> >
> > I haven't been to CHM before, and am looking forward to spending an
> extended period of time there.
> >
> > What I'm asking for is help/recommendations in terms of a good hotel to
> stay at that is relatively close to the museum.  I don't want to be in a
> luxury hotel, nor do I want to be in a dive.
> > I'd also like to be in a place that has a restaurant relatively close by
> (preferably within walking distance) that I could get some decent meals
> (breakfast/dinner) while I'm there.
> >
> > Unless this is a topic of general interest to the group, it'd probably
> be best to reply to me directly rather than post responses to the list.
> >
> > Many thanks,
> > -Rick
> > --
> > Rick Bensene
> > The Old Calculator Museum
> > http://oldcalculatormuseum.com
> >
>
>
> I'd also be interested in any recommendations, so might as well list-post,
> it'll be of value to a couple of us.
>
> Last I was there was this time of year in 2014 and I really should get
> back (spent the entire day there and never saw it all). Having IHG points
> to use, I found a Holiday Inn Express in Belmont that didn't charge an arm
> and a leg (14 miles from CHM) that was clean and comfortable and I found it
> an easy walk to several restaurants. One bit of advice, some of the live
> exhibits, like the 1401 demo, only run on certain days, so check the CHM
> calendar in advance if there's something you absolutely want to see live.
> -Cory
>
>

Re: Trip to CHM - Hotel/Restaurant Advice

[CuriousMarc via cctalk]

I'd look at hotels on El Camino in Mountain View or Palo Alto, maybe near San 
Antonio road. There are a whole bunch of smaller hotels along there. Warning: 
this is California, Silicon Valley and more specifically Google land, so hotels 
tend to be full and rather expensive for what they are, as you'd expect. Also 
plenty of restaurants along El Camino, and in Mountain View on Castro street. 
Booking.com is your friend. The food options in the museum are limited, but 
just across the street there are more choices ranging from Starbucks to fancy 
South American, all good.

Beware, the Museum is closed Mondays and Tuesdays. Live demos of the IBM 1401 
are on Wednesdays 3 pm and Saturdays 11 am. The PDP-1 is demoed more rarely, on 
some Saturdays in the afternoon. More details here:
http://www.computerhistory.org/hours/

Send me an email when you are around. I usually am at the museum on Wednesdays 
working on the 1401 with the restoration team before the official demo. I'd 
love to give you a special tour of the exhibit (and discuss old computers and 
calculators!).

Marc

> On Mar 30, 2017, at 3:19 PM, Cory Heisterkamp via cctalk 
>  wrote:
> 
> 
> 
>> On Mar 30, 2017, at 4:17 PM, Rick Bensene via cctalk wrote:
>> 
>> Hello, all,
>> 
>> In mid-June, I am planning a trip to Mountain View for two days to visit the 
>> Computer History Museum.
>> 
>> I plan on flying out of Portland early AM on June 14, checking into hotel, 
>> then heading straight to the museum for the day.
>> I will go back to the hotel for the evening, and return to the museum on the 
>> 15th, and stay into early afternoon, and then check out of the hotel and 
>> head to the airport to return home.
>> 
>> I haven't been to CHM before, and am looking forward to spending an extended 
>> period of time there.
>> 
>> What I'm asking for is help/recommendations in terms of a good hotel to stay 
>> at that is relatively close to the museum.  I don't want to be in a luxury 
>> hotel, nor do I want to be in a dive.
>> I'd also like to be in a place that has a restaurant relatively close by 
>> (preferably within walking distance) that I could get some decent meals 
>> (breakfast/dinner) while I'm there.
>> 
>> Unless this is a topic of general interest to the group, it'd probably be 
>> best to reply to me directly rather than post responses to the list.
>> 
>> Many thanks,
>> -Rick
>> --
>> Rick Bensene
>> The Old Calculator Museum
>> http://oldcalculatormuseum.com
> 
> 
> I'd also be interested in any recommendations, so might as well list-post, 
> it'll be of value to a couple of us. 
> 
> Last I was there was this time of year in 2014 and I really should get back 
> (spent the entire day there and never saw it all). Having IHG points to use, 
> I found a Holiday Inn Express in Belmont that didn't charge an arm and a leg 
> (14 miles from CHM) that was clean and comfortable and I found it an easy 
> walk to several restaurants. One bit of advice, some of the live exhibits, 
> like the 1401 demo, only run on certain days, so check the CHM calendar in 
> advance if there's something you absolutely want to see live. -Cory
> 

Re: Trip to CHM - Hotel/Restaurant Advice

[jim stephens via cctalk]

On 3/30/2017 6:58 PM, CuriousMarc via cctalk wrote:

Beware, the Museum is closed Mondays and Tuesdays. Live demos of the IBM 1401 
are on Wednesdays 3 pm and Saturdays 11 am. The PDP-1 is demoed more rarely, on 
some Saturdays in the afternoon. More details here:
http://www.computerhistory.org/hours/

Marc,
I'll also look you up if we are there mid week.

As to recommendations, I like the Country Inn & Suites by Carlson in 
Sunnyvale, which is at Ca 237 and Caribbean.  If you run around by the 
bay is Weird Stuff, and it is about 2 or so miles from the CHM.  At 237 
Caribbean becomes Lawrence which is a handy road since you can easily 
get to Halted for another stop.  Their new spot is quite a bit better 
stocked than the original location.


I'm not sure Fry's is worth a stop, unless you don't have one and want 
to see what they have.


Country Inn
1300 Chesapeake Terrace, Sunnyvale, CA 94089

Charles might chime in about the place he stayed while here for VCF if 
he sees this, that hotel seemed good, though I don't recall where it was.


I really like Tomatina's for Italian, though it's a drive.  We stumbled 
across it and were highly impressed with the food.

3127 Mission College Blvd, Santa Clara, CA 95054

I'm in Southern, Ca, and travel up there a time or two a year, FWIW.
Thanks
Jim

Re: Cross-talk square-wave?

[David Bridgham via cctalk]

> It's not clear C-coupling is what's going on here (the wave shape looks 
> pretty sharp for what I understand of the circuit/layout).
> Notably though, C-coupling would remove any DC bias, but David's screen shot 
> indicates a DC bias on the line.
>
> Is this line currently connected to the FPGA, or is it just the wire and R?
> Perhaps the bias is coming from the FPGA, with C-coupling of the wave via the 
> wire.
> Or perhaps it's all crosstalk from within the FPGA, 'visible' because of the 
> high load R.

Yes, the wire is connected to the FPGA at one end.  That FPGA I/O pin is
*supposed* to be configured for high-Z but that's the only place I can
see the DC bias coming from.

> If the wire and FPGA pin are connected, separate them (reduce the wire 
> circuit to just the wire and R to GND): see whether the DC bias and/or the 
> square wave disappear.

Because of the way it's built, I'm not seeing a reasonable way to
disconnected the FPGA while leaving the rest intact.  However, I did
move the signal to another wire in the ribbon cable and the problem is
basically gone.  This lets me move on with other issues but am still a
bit puzzled with this one.

Re: Trip to CHM - Hotel/Restaurant Advice

[Chuck Guzis via cctalk]

On 03/30/2017 08:04 PM, jim stephens via cctalk wrote:
> As to recommendations, I like the Country Inn & Suites by Carlson in 
> Sunnyvale, which is at Ca 237 and Caribbean.  If you run around by
> the bay is Weird Stuff, and it is about 2 or so miles from the CHM.
> At 237 Caribbean becomes Lawrence which is a handy road since you can
> easily get to Halted for another stop.  Their new spot is quite a bit
> better stocked than the original location.


Bonus points for those who remember their original original location.

--Chuck

Re: Trip to CHM - Hotel/Restaurant Advice

[Al Kossow via cctalk]

On 3/30/17 8:15 PM, Chuck Guzis via cctalk wrote:
> On 03/30/2017 08:04 PM, jim stephens via cctalk wrote:
>> As to recommendations, I like the Country Inn & Suites by Carlson in 
>> Sunnyvale, which is at Ca 237 and Caribbean.  If you run around by
>> the bay is Weird Stuff, and it is about 2 or so miles from the CHM.
>> At 237 Caribbean becomes Lawrence which is a handy road since you can
>> easily get to Halted for another stop.  Their new spot is quite a bit
>> better stocked than the original location.
> 
> 
> Bonus points for those who remember their original original location.
> 
> --Chuck
> 

Phelen Ave in San Jose, which was before the larger place on Sycamore in 
Milpitas.

Richard Anderson had several places after he, Mac McDougal and the Schutz's 
started WSW.
The Weird Stuff name and logo came from Richard's brother, who was in the
advertising business.

Re: Trip to CHM - Hotel/Restaurant Advice

[jim stephens via cctalk]

On 3/30/2017 8:15 PM, Chuck Guzis via cctalk wrote:

Bonus points for those who remember their original original location.

--Chuck


Halted?  We drove by there, could get address off google.

Weird Stuff used to be across from the original Frys, then Frys move 
across the street with the Giant IC building.  Again, can drive there, 
would have to do it on google to get the address.


Extra points if you remember the IC supplies in the original Frys next 
to the M&M's and cans of Pringles.  Before the brothers decided if they 
were an electronics store or a stereo store and had fights.


Across from the side of the road that original Frys was on was a TOGO's 
that filled the parking lot and 2 or three nicely stocked junk stores, 
which changed frequently.  The guys who did the Hard Disk drive guide 
book had their original store in there and lots of cheap and hard to 
find product.


thanks
Jim

Re: Trip to CHM - Hotel/Restaurant Advice

[jim stephens via cctalk]

On 3/30/2017 8:15 PM, Chuck Guzis via cctalk wrote:

Bonus points for those who remember their original original location.

--Chuck

General area of lots of good junking back in the day was here.  I think 
Halted is the last one of
the originals to leave.  They moved to a place on Ryder and that was 
where they were for a very

long time.  of course they are up off Corvin now.

https://goo.gl/maps/EYAbqVjoC3B2

Thanks
jim

Re: Trip to CHM - Hotel/Restaurant Advice

[Fred Cisin via cctalk]

Bonus points for those who remember their original original location.


Across from the side of the road that original Frys was on was a TOGO's that 
filled the parking lot and 2 or three nicely stocked junk stores, which 
changed frequently.  The guys who did the Hard Disk drive guide book had 
their original store in there and lots of cheap and hard to find product.


"Computer Literacy"

Re: Trip to CHM - Hotel/Restaurant Advice

[Al Kossow via cctalk]

On 3/30/17 8:35 PM, Fred Cisin via cctalk wrote:
>The guys who did the Hard Disk drive guide book had their
>> original store in there

Corporate Systems Center
their main office was on Maude

Re: Trip to CHM - Hotel/Restaurant Advice

[Fred Cisin via cctalk]

On Thu, 30 Mar 2017, jim stephens via cctalk wrote:
Across from the side of the road that original Frys was on was a TOGO's that 
filled the parking lot and 2 or three nicely stocked junk stores, which 
changed frequently.  The guys who did the Hard Disk drive guide book had 
their original store in there and lots of cheap and hard to find product.


Corporate Systems Center  Martin Bodo?  "The Hard Drive Bible"

Re: Cross-talk square-wave?

[Jon Elson via cctalk]

On 03/30/2017 10:07 PM, David Bridgham via cctalk wrote:

It's not clear C-coupling is what's going on here (the wave shape looks pretty 
sharp for what I understand of the circuit/layout).
Notably though, C-coupling would remove any DC bias, but David's screen shot 
indicates a DC bias on the line.

Is this line currently connected to the FPGA, or is it just the wire and R?
Perhaps the bias is coming from the FPGA, with C-coupling of the wave via the 
wire.
Or perhaps it's all crosstalk from within the FPGA, 'visible' because of the 
high load R.

Yes, the wire is connected to the FPGA at one end.  That FPGA I/O pin is
*supposed* to be configured for high-Z but that's the only place I can
see the DC bias coming from.
Don't trust ANYTHING!  Recent Xilinx FPGAs have permanent 
"weak keepers" on all pins, they can not be turned off.
What this is is a non-inverting receiver on the pad, that is 
driving back to the pad with about a 50K Ohm resistor.
Plays hob with analog stuff like crystal oscillators.  The 
weak keeper would PERFECTLY explain your square wave!
When it gets a narrow pulse to high, it holds the line 
high.  When it gets a narrow pulse to low, it will switch to 
holding the line low.  So, if you are using a Xilinx FPGA of 
recent vintage, or some of their CPLDs, they will do exactly 
this.


Jon

Re: Trip to CHM - Hotel/Restaurant Advice

[Bob Rosenbloom via cctalk]

On 3/30/2017 8:42 PM, Fred Cisin via cctalk wrote:

On Thu, 30 Mar 2017, jim stephens via cctalk wrote:
Across from the side of the road that original Frys was on was a 
TOGO's that filled the parking lot and 2 or three nicely stocked junk 
stores, which changed frequently.  The guys who did the Hard Disk 
drive guide book had their original store in there and lots of cheap 
and hard to find product.


Corporate Systems Center  Martin Bodo?  "The Hard Drive Bible"



Corporate Systems Center, and Martin, still exist, as Digital Loggers, 
on Walsh Av. I still work there, 20+ years...


Bob


--
Vintage computers and electronics
www.dvq.com
www.tekmuseum.com
www.decmuseum.org

Re: Cross-talk square-wave?

[Tony Duell via cctalk]

On Thu, Mar 30, 2017 at 9:13 PM, Noel Chiappa via cctalk
 wrote:
> I'm still not clear, from the discussion, how exactly that nice 'square-wave'
> interference is happening - could it be capacitative crosstalk? (I'd have
> thought capacitative cross-talk would be inverted - driving a positive voltage
> on one 'side' of the 'capacitor' would, I would think, induce an oppposing
> voltage on the other. But I'm clearly no EE! :-)


The fundamental rule is 'You can't change the voltage across a capacitor
instantly'. There is a related one 'You can't change the current through
an inductor instantly'. It (of course) doesn't matter if said capacitor
or inductor is an actual component or 'strays'.

So instantaneously, a capacitor acts like a constant voltage drop.
If the charge on the capacitor doesn't change much (fast signals,
high resistors so not much current flow), the 2 sides of the
capacitor will be much the same signal (possibly with a
constant voltage offset).

-tony

RE: Trip to CHM - Hotel/Restaurant Advice

[Rich Alderson via cctalk]

From: Rick Bensene
Sent: Thursday, March 30, 2017 2:18 PM

> What I'm asking for is help/recommendations in terms of a good hotel to
> stay at that is relatively close to the museum.  I don't want to be in a
> luxury hotel, nor do I want to be in a dive.  I'd also like to be in a
> place that has a restaurant relatively close by (preferably within
> walking distance) that I could get some decent meals (breakfast/dinner)
> while I'm there.

There aren't a lot of hotels in Mountain View, and what there are are not
easily within walking distance of good food (In 'n' Out does not qualify).
Most are on El Camino Real.  Looking at one which I have used (Hilton
Garden Inn) for relative pricing, it's not available for your dates and
all the others I would point you towards are in the $250-$400/night range.
This is the heart of Silicon Valley, after all, and lots of business travel
ends up in these places.

You're at the height of the tourist season, too.  The place I stayed last
weekend in Milpitas for $130/night is $260 for your travel dates.

Sorry for not being terribly helpful.

Rich

Rich Alderson
Vintage Computing Sr. Systems Engineer
Living Computers: Museum + Labs
2245 1st Avenue S
Seattle, WA 98134

mailto:ri...@livingcomputers.org

http://www.LivingComputers.org/

Re: Cross-talk square-wave?

[allison via cctalk]

On 03/30/2017 06:01 PM, Brent Hilpert via cctalk wrote:
> On 2017-Mar-30, at 1:13 PM, Noel Chiappa via cctalk wrote:
>>> From: Allison
>>> FYI this is the same problem designers hit with DRAMS back 40 years ago.
>> This didn't ring (pun not intended) a bell for me; can you say a bit more?
>>

Early Dram memories were fickle to design and many poor designs got out
with notable consequences.  Examples wer common in the S100 realm and
others too.  The MITS 88-4K was replaced with 88-S4K for that reason it was
that bad and that was using the non-multiplexed 22 pin 4K parts.   The
later 16K
multiplexed 16 pin parts 4116 were worse Tandy TRS80 EI version 1(no buffer)
and 2(buffered cable) leading to the later third try a complete redesign.

The problem was a high capacitance load of many NMos Drams and the
address and
data drive.  The fix was not trivial.  A fairly hard source like a
74S157 (treat as similar
in this case to a voltage source) provides a fast stepped input to a
signal line and
if the line were terminated in its characteristic impedance it would
simply transfer
the signal and preserve waveform.  But an array of 16 DRAM for one
address line
with board and input capacitance looks like a roughly 160pf capacitor to
ground.
Your S157 switches and a step waveform goes from ground to +2.7V (lets say)
and the instantaneous current is rather large with an exponential decay. 
Since the line does not see a termination like its characteristic
impedance or
anything acceptable much of the energy in the pulse is reflected back
and you
see ringing or waveform distortion (depends on length of the line).  So
the then
simple fix was series resistance by experimental (maybe empirical too)
testing
for the best waveform and timing compromise.  Usually this lead to both
re-layout
of the board as when you get 8 or 9 lines doing this the ground gridding
starts
showing  noise too.  In the end its all transmission lines that have
poor termination.

What people often forget at DC and very low frequencies the MOS/CMOS
input are
essentially open circuits.  At high frequencies (pulse rates) its a
capacitor which is
an energy storage device.  Changing that voltage across the cap takes
energy and
time and is not a friendly load by any cable/transmission line.

So putting a SD or even a CF at the end of a ribbon or spectra cable
without adequate
grounds (every other wire or a backplane ground) means the field around
those
wires will couple and be the fields around its neighbours and make
itself known in
the most offensive ways.

For those that have forgotten those that forget history will relive it.

*Vonada's Engineering Maxims* are a group of pithy observations about
computer engineering
compiled by Don Vonada, an engineer at DEC
, and reproduced in:

  * C. Gordon Bell, J. Craig Mudge, John. E. McNamara, "/Computer
Engineering/"

They are:

 1. There is no such thing as ground.
 2. Digital circuits are made from analog parts.
 3. Prototype designs always work.
 4. Asserted timing conditions are designed first; unasserted timing
conditions are found later.
 5. When all but one wire in a group of wires switch, that one will
switch also.
 6. When all but one gate in a module switches, that one will switch also.
 7. Every little pico farad has a nano henry all its own.
 8. Capacitors convert voltage glitches to current glitches
(conservation of energy).
 9. Interconnecting wires are probably transmission lines.
10. Synchronizing circuits may take forever to make a decision.
11. Worse-case tolerances never add - but when they do, they are found
in the best customer's machine.
12. Diagnostics are highly efficient in finding solved problems.
13. Processing systems are only partially tested since it is impractical
to simulate all possible machine states.
14. Murphy's Laws apply 95 percent of the time. The other 5 percent of
the time is a coffee break.



Allison

>>> From: Chuck Guzis
>>> I'll offer a suggestion that if your SD card *must* be a significant
>>> distance from its host
>> Like I said, this is a pre-prototype; on the production units, there will be
>> _no_ cable. The SD socket will be about 1-2" from the FPGA.
>>
>>> From: Dwight Kelvey
>>> this behavior on my PDP-8/e where a 7474 flip flop chip was bad. The
>>> input looked great and the output was "half baked"
>> There's no chip at all on the driving end of the line (just that 470K
>> resistor); we see this with the SD card _unplugged_. And we see the exact
>> same thing on several lines.
>>
>>
>> I'm still not clear, from the discussion, how exactly that nice 'square-wave'
>> interference is happening - could it be capacitative crosstalk? (I'd have
>> thought capacitative cross-talk would be inverted - driving a positive 
>> voltage
>> on one 'side' of the 'capacitor' would, I would think, induce an oppposing
>> voltage on the other. But I'm clearly no EE! :-)
> I don't have a full enough picture of the circuit

Re: Trip to CHM - Hotel/Restaurant Advice

[George Rachor via cctalk]

I have that book!

George Rachor

> On Mar 30, 2017, at 8:56 PM, Bob Rosenbloom via cctalk 
>  wrote:
> 
> On 3/30/2017 8:42 PM, Fred Cisin via cctalk wrote:
>> On Thu, 30 Mar 2017, jim stephens via cctalk wrote:
>>> Across from the side of the road that original Frys was on was a TOGO's 
>>> that filled the parking lot and 2 or three nicely stocked junk stores, 
>>> which changed frequently.  The guys who did the Hard Disk drive guide book 
>>> had their original store in there and lots of cheap and hard to find 
>>> product.
>> 
>> Corporate Systems Center  Martin Bodo?  "The Hard Drive Bible"
>> 
>> 
>> 
> Corporate Systems Center, and Martin, still exist, as Digital Loggers, on 
> Walsh Av. I still work there, 20+ years...
> 
> Bob
> 
> 
> -- 
> Vintage computers and electronics
> www.dvq.com
> www.tekmuseum.com
> www.decmuseum.org
> 

Re: Trip to CHM - Hotel/Restaurant Advice

[Chuck Guzis via cctalk]

On 03/30/2017 08:31 PM, Al Kossow via cctalk wrote:

> Phelen Ave in San Jose, which was before the larger place on Sycamore
> in Milpitas.

In the late 70s, on Evelyn in Sunnyvale, near Wolfe, I believe.   I
could check my old records.

I recall when John Fry opened his store, the big seller was Canfield's
Diet Chocolate Fudge Soda.   I thought it was dreadful, but people
bought it by the caselot.  Fry's had a lot of Everex PC boards, much of
which was probably returns.   And you could buy a VME system there also.

I still have various connectors and whatnot in the little poly bags with
the red and white Fry's labels on them.

I bought my turntable and soldering iron tips at Sunnyvale Electronics.
Points for those who can tell me where that was.

I suspect that if I returned for a visit after nearly 30 years, I'd get
lost.

--Chuck

Re: Trip to CHM - Hotel/Restaurant Advice

[Fred Cisin via cctalk]

On Thu, 30 Mar 2017, Chuck Guzis via cctalk wrote:

I recall when John Fry opened his store, the big seller was Canfield's
Diet Chocolate Fudge Soda.   I thought it was dreadful, but people
bought it by the caselot.  Fry's had a lot of Everex PC boards, much of
which was probably returns.   And you could buy a VME system there also.

I still have various connectors and whatnot in the little poly bags with
the red and white Fry's labels on them.

I bought my turntable and soldering iron tips at Sunnyvale Electronics.
Points for those who can tell me where that was.

I suspect that if I returned for a visit after nearly 30 years, I'd get
lost.


. . . and it would be very depressing.

It's been more than three decades since the staffing at Fry's went bad.

Re: Trip to CHM - Hotel/Restaurant Advice

[Chuck Guzis via cctalk]

On 03/30/2017 08:56 PM, Bob Rosenbloom via cctalk wrote:

> Corporate Systems Center, and Martin, still exist, as Digital
> Loggers, on Walsh Av. I still work there, 20+ years...

I still have the manuals and software for his Fastcache and Fastecache
32 SCSI controllers.  Got rid of the cards themselves a long time ago
when better cards became available and 30-pin SIMMs were no longer popular.

I think I still have a system around here with an ESDI drive that I got
from him.  There was another lesser-known outfit (the name escapes me)
in Sunnyvale that offered cut-rate deals on big hard drives.

And of course,  the business retail outfits, Inmac with its trademark
blue cables.   TI had a retail store in Stanford Shopping Center.

And if you couldn't find a part you needed, a few beers at the Walker's
Wagon Wheel in Mountain View after work would turn up someone who could
filch what you needed from their stock at work.

Remember Haltek in Mountain View?  (wasn't it at the dead end of Linda
Vista?  I bought my Tek 465 there.)

What was the name of the warehouse operation in Palo Alto that just had
stacks of stuff with no particular organization?  I bought a lot of
cable there.

I remember the smell of tomato sauce that pervaded Sunnyvale in the
summertime and all of the seasonal cannery workers. The cherry blossoms
that would make piles in the streets come springtime. Santa Clara may
have had Italian prunes, but Sunnyvale had cherry orchards.

Remember Chez Yvonne in Mountain View on El Camino with its geriatric
waitresses that would call you Shveetie and Yvonne herself holding court?

When a bunch of us got Durango started on 10101 Bubb Road in Cupertino,
there were canneries in back, just across the railroad tracks in Monte
Vista.   Some kids had the building space across the road trying to get
a little outfit called "Apple" started.   Wonder how that worked out...

After being gone for almost 30 years, I'd probably get lost now.  And,
as Thomas Wolfe said, "You can't go home again."

--Chuck

Re: Cross-talk square-wave?

[Chuck Guzis via cctalk]

On 03/30/2017 09:07 PM, Tony Duell via cctalk wrote:


> The fundamental rule is 'You can't change the voltage across a
> capacitor instantly'. There is a related one 'You can't change the
> current through an inductor instantly'. It (of course) doesn't matter
> if said capacitor or inductor is an actual component or 'strays'.

Funny that driving DRAMs would be mentioned today.   Yesterday, I was
going through some of my old tubes of ICs and ran across some AM2966
DIPs.  I didn't remember why I'd gotten them or even what they were.

A glance at a datasheet  refreshed my memory--basically they're LS244
octal drivers intended for MOS memory address lines.  They feature 25
ohm resistors in the collectors of both of the totem-pole output
transistors.  Each output is spec-ed to sink a minimum of 50 ma.

It takes some muscle to drive a capacitive load.

--Chuck

Re: Cross-talk square-wave?

[Mark Linimon via cctalk]

On Thu, Mar 30, 2017 at 07:41:25PM -0400, allison via cctalk wrote:
> *Vonada's Engineering Maxims* are a group of pithy observations about
> computer engineering

There's too much hard-learned truth in all that, to be funny.

mcl