test-drb

test-drb@ccmp.vtda.org

101090 discussions

by jnc＠mercury.lcs.mit.edu

> 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

8 years, 10 months

Anyone want a Sun T-shirt?

by cclist＠sydex.com

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

8 years, 10 months

Cross-talk square-wave?

by jnc＠mercury.lcs.mit.edu

Hi, a question about generic analog stuff. In the process of getting SD cards to work, Dave is seeing square-wave noise on a line. (1V of square wave, with pulses about 400ns long, running at 375kHz.) The line runs through a flat cable of modest length, along with other signal-carrying lines. (No, we were not smart, and didn't put ground lines between each pair of signal lines!) Could cross-talk cause this kind of noise? We would have thought that you'd only get spikes, associated with the rising and trailing edges of a signal in a parallel wire, not a whole square-wave. During the constant-current period in the middle of the pulse, there shouldn't be any cross-talk? Is there some mechanism I/we don't understand that could do that? (My guess is there's a leakage path in the circuitry on one end or the other, not cross-talk in the cable, but...) Thanks! Noel

8 years, 10 months

Wyse keyboards and their variants

by sales＠elecplus.com

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

8 years, 10 months

Floating point routines for the 6809

by spc＠conman.org

Some time ago I came across the MC6839 ROM which contains floating point routines for the 6809. The documentation that came with it stated: Written for Motorola by Joel Boney, 1980 Released into the public domain by Motorola in 1988 Docs and apps for Tandy Color Computer by Rich Kottke, 1989 What I haven't been able to find is the actual *source code* to the module. Is it available anywhere? I've been playing around the the MC6839 on an emulator but having the source would clear up some issues I've been having with the code. -spc

8 years, 10 months

QIX game on PDP-11

by henk.gooijen＠hotmail.com

Hi PDP-11 game players ? I found that the famous QIX game was ported to the PDP-11 !! See http://imgur.com/a/gtPfh Back in the days, I spend quite a few Guilders on this addictive game. Does anybody have a lead to the software? That would be awesome! Thanks, Henk

8 years, 10 months

Cross-talk square-wave?

by jnc＠mercury.lcs.mit.edu

> From: Eugene (W2HX) > I am still not convinced it is coupling at all. ... I just don't think > you can get square waves from square waves. ... > 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 ... > Looking at this picture ... 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. Exactly. That sort of cross-talk we understand (and have seen before). But a square wave? How can that be? That was the motivation for my original post. It's not super-critical to understand, because like I said, this is on a pre-prototype, and the actual unit will be arranged nothing like this (no cable, etc, etc), so we're just going to fix this with whatever kludge makes it go away, so we can focus on the things we really do need to work on. But we'd still like to understand what is happening here, and how. Could cross-talk (of whatever form, inductive or capacitive) do this, or does this more or less have to be signal leakage (on the board at one end, or the other) somehow? Noel

8 years, 10 months

Model 28 Teletypes in Edmonton, Alberta

by rlloken＠telus.net

On Wed, 29 Mar 2017, W2HX wrote: > I might have missed it, but did you offer this on the greenkeys list (or > would you like me to forward it?) they are tty enthusiasts. Eugene No, I have never been a member of the green keys list and there is no point in joining now. Punt the message to the green keys list if you can. I still have (because they are small and portable) a set of model 28 service manuals, a keyboard assembly, a print mechanism (a carriage assembly?), a box of unperforated five level tape rolls, and a few unused but quite elderly ribbons if anybody has a use for them. -- Richard Loken VE6BSV : "...underneath those tuques we wear, Athabasca, Alberta Canada : our heads are naked!" ** rlloken at telus.net ** : - Arthur Black

8 years, 10 months

Model 28 Teletypes in Edmonton, Alberta

by rlloken＠telus.net

So, my ex-wife sent my Model 28 RO and Model 28 ASR (along with a Conn vacuum tube electronic organ) to the landfill yesterday. I am told by my son that they went to the Eco Station Reuse Area at either the Ambleside or kennedale Eco Station. So, in the unlikely event that somebody wanting a 28 tty and within travelling distance of Edmonton, Alberta reads this, those items are reported to be there for taking. Oh, and bring a truck and a very strong friend. -- Richard Loken VE6BSV : "...underneath those tuques we wear, Athabasca, Alberta Canada : our heads are naked!" ** rlloken at telus.net ** : - Arthur Black

8 years, 10 months

Apple 1, Commodore 65, Enigma Machine, Inventor of C++

by cctalk＠snarc.net

"What do an Apple 1, Commodore 65, Enigma Machine, and the inventor of C++ all have in common?" "They all be at VCF East this weekend." You should go, too. ________________________________ Evan Koblentz, director Vintage Computer Federation a 501(c)3 educational non-profit evan at vcfed.org (646) 546-9999 www.vcfed.org facebook.com/vcfederation twitter.com/vcfederation

8 years, 10 months

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