test-drb

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101090 discussions

by bpettitx＠comcast.net

Chuck Guzis <cclist at sydex.com> wrote: Subject: Re: Control Data 160 Ebay I believe the eBay lister stated that it was a 160, not the -A. So no return jump for you... --Chuck Which would make it even more scarce. There were only a little over a 100 of the 160 models made. And 40+ of them were rebranded as NCR machines. There were 495 160-As made officially. (There were also a small number shipped without serial numbers to the good people at Langley.) I know of at least 5x 160-As still in existence, besides my own. Which should be going to a museum this week if they can sort out shipping glitches. My system includes a 161-A Typewriter in lousy shape and a 167-2 Card Reader in perfect shape. Plus all manuals, software (with listings) and spare parts. Even the paper tape rewinder! I did not know any 160 machines survived, so who ever bought it has a unique item. I have looked for 15 years for an 8092 = the first true 8 bit computer. Haven't found even a hint or rumor of one. I am working with Al Kossow, to see that this material is eventually in his archives. Billy Pettit

10 years, 11 months

Zendex ZX-200A firmware reverse-engineered

by spacewar＠gmail.com

The original proprietor of Zendex has put the firmware of the ZX-200A in the public domain, so I've put my reverse-engineered source code on Github: https://github.com/brouhaha/zx200a-fw The ZX-200A is a single-board Multibus floppy controller intended for Intel MDS (including Series II and Series III) development systems, replacing either or both the Intel dual-board SBC 201 single-density and SBC 202 double-density floppy controllers. Since it can do both densities, it can replace both Intel controllers simultaneously, allowing the same floppy drives to be used for either density, by using different logical drive numbers. We take it for granted that "modern" floppy controllers often support selectable density, but with those early Intel board-level floppy controllers that wasn't the case. Also, the Intel SBC 202 double-density controller uses an Intel-proprietary M2FM disk format, instead of IBM-compatible MFM. As such, none of the single-chip FDCs are compatible with it, with the possible exception of the Western Digital 1781 (with a huge pile of external support logic), and (less likely) the TI TMS9909. Unfortunately the original ZX-200A manual, which contained the schematics and source code, is not available, hence my project to reverse-engineer it. I'm working on tracing out the schematic, but as the board has 82 chips it is slow going.

10 years, 11 months

Problems with 8/A Programmer's Panel

by charlesmorris800＠centurytel.net

Several years ago, Vince Slyngstad and I "cloned" the rare DKC8-AA Programmer's Panel for PDP-8 with some improvements (0.6 vs. 0.3" LED displays, real "click" buttons instead of that membrane keypad, and fixed a couple of bugs in the original design). Also, since 8235's were scarce even then, we used 74F244 buffers instead to gate the input vs. output of the switch register onto the bus back to the M8316 Option 1 board. That may have caused a lurking problem, since occasionally the SR will change bits when an address is loaded. Turns out an oscillation starts on the ground lines at about 20 MHz with certain entries at the keypad to LSR and LA (I can't see an obvious pattern). This parasitic is large enough (up to 2V p-p with respect to the chassis/rack) that it's clocking the D-flops used as the physical switch register! It can be seen in the 7-segment displays as a "flicker" which will change when I touch the ground on the board... attempts to add more grounds actually made the problem worse! I'm thinking of redoing the board layout with better attention to ground planes/power buses. There's a .01 uf decoupling cap at every IC and 12 out of 40 pins on each of the two connecting ribbon cables are dedicated to ground. 7 on one, 5 on the other are for +5 volts. On the other hand, I am tired of tinkering and considering just buying a real DKC8-AA if there's one out there. Anyone? ;) -Charles

10 years, 11 months

New BBS in Maryland

by mokuba＠gmail.com

+1-410-734-6804 New hobby thing. ;) Wildcat! 4 running on it, stock out of box config. If you don't see all the menus except for help and send to sysop, wait till I validate users. When I get back home i'll set it to give non-validated users more permissions, though. -- Gary G. Sparkes Jr. KB3HAG

10 years, 11 months

IBM 026

by misc4email＠yahoo.com

Can anyone help me to locate an old IBM 026 printing keypunch for a project on which I am working?I was an IBM Field Engineer many years ago and I used to service lots of Unit Record equipment at that time.Any help in locating a machine would be greatly appreciated.Thank you. AlEx-IBM Field Engineer

10 years, 11 months

Schematics KDJ11-A / M8192?

by jnc＠mercury.lcs.mit.edu

> From: Holm Tiffe > Anyway, thanks for the schematics Eh, de nada. > I have the board running again. The fix was simple, the xtal was bad. You're lucky it was something so simple! (Although we've seen this kind of thing before - I had that 11/23 with a bad crystal.) I've got three dead 11/73 boards (from someone else), but none of them are that easy. Different symptoms on all three, but I suspect the State Sequencer gate array on all three. On one, at least, the ILOE latch control signal from that gate array is sitting at 2V (which I seem to recall is characteristic of a TTL input that's not being driven). Maybe it's just some corrosion, and re-seating the gate array (if I can work out how to unseat it - don't have the extraction tool) will fix it. Otherwise, I'm SOL. At least the J11 there are spares for - that gate array is surely umobtainium. Noel

10 years, 11 months

BBC Model B with Raspberry Pi Internals

by mark＠wickensonline.co.uk

Bit of a tricky one to google this, so thought I'd consult the list - does anyone know of a documented project that replaced the internals of a BBC Model B with a Raspberry Pi (or MiniITX PC) interfacing with keyboard etc. to bring modern internals with a traditional interface? I don't even know if there is a word for these kind of projects? Thanks, Mark.

10 years, 11 months

A poltergeist in my machine?

by jnc＠mercury.lcs.mit.edu

So I've mentioned how I've seen this wierd behaviour where QBUS memory boards that hadn't been used in a long time didn't work when first plugged in, but started working later. I just had something even weirder happen, and am curious if anyone has an plausible explanations. So I had a dead M8044 (MSV11-D), symptom was that you could write -1 to any location, it read back as 0. Quite repeatable, I can power cycle the machine, take the card in and out, etc, etc. So I throw it on an extender, and start chasing. I have a two instruction loop (write location 0, loop), and I'm watching the data going into the memory chips on the card, and it all looks good. So I add a third instruction (read location 0, after the write), and continue chasing. Data looks good coming out of the chips; then it goes to an octal latch. So I look at the latch enable, and that doesn't look so hot - just a tiny little ugly spike. So I look at the source of that, and it's a D flop. So I look at the D flop's clock input, and it's also a nasty little spike. So that comes >from the output of a triple-AND, and so I start looking at the inputs of the 3-AND. And when I put my 'scope lead on the second input... the memory suddenly starts working! Well, I could see that - the added resistance or capacitance or whatever of the probe might have had some effect on a circuit that was right on the edge. But here's where the ghost enters the machine. I pull the 'scope probe ..... and the memory keeps working! I can power cycle the machine, leave it off for 15 minutes, power it back on - and the memory still works fine! Does anyone have _any_ idea WTF is going on here?!?! I feel like I'm in some sort of AI koan... Noel

10 years, 11 months

21MX proms (per request)

by marc.verdiell＠gmail.com

Thanks for the answers everyone, I am writing everything down... Marc

10 years, 11 months

Control Data ad: Omega 480 "370 compatible alternative" on eBay

by linimon＠lonesome.com

http://www.ebay.com/itm/VINTAGE-197X-RARE-CONTROL-DATA-AD-OMEGA-480-370-COM… Not that I'm going to bid on it, but ... I had never heard of this CDC product before. Does anyone have any idea if this was a real product, or just a way to poke IBM in the eye, or what? mcl

10 years, 11 months

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