test-drb November 2017

test-drb@ccmp.vtda.org

126 participants
149 discussions

by billdegnan＠gmail.com

This looks to me like the power supply and backplane of a PDP 11/05, looks to be in nice shape. Surprised no one grabbed this yet, esp someone with an 11/05 that has issues with power supply. Someone might have the missing parts. "DEC PDP-11 Digital BA11-KE Mounting Box" https://www.ebay.com/itm/DEC-PDP-11-Digital-BA11-KE-Mounting-Box/28265372079 granted "all you need are the cards and the front panel" reminds me of the steve martin routine. "It's easy to be a millionaire, first get a million dollars and then ...." Compare with http://vintagecomputer.net/browse_thread.cfm?id=622 b

7 years, 1 month

Slightly OT: Computer internals book recommendations

by echristopherson＠gmail.com

The fascinating discussion Jim just started on buses got me thinking again about a book I've been trying to track down for a while. While it's not necessarily classic-computing-oriented, it's not really about newfangled computers either; heck, I encountered it in 2003 or so, so it'd be pretty dated by now. Basically, I'm looking for a certain book (although really any book in the same vein would satisfy), which was on computer system architecture, organization, etc.; it talked about the usual boolean logic, assembly programming in some fictitious instruction set, an overview of two actual architectures (I think at that time they were 32-bit x86 and 64-bit POWER). The other thing I remember very specifically was there was a place near the back (probably an appendix) that talked about one or more specific buses (I think at least PCI was there), with timing diagrams to tell you what was actually going back and forth between the bus and CPU. Like I said, I'm sort of keen on finding the exact book I had, but I realize that's somewhat unrealistic, so I'm open to recommendations on any book like that. And if it can cover the relavant concepts for both classic and newish computers, that would be great. Basically what I hope to learn is how you actually deal with peripherals, add-in cards, etc., on the assembly language level, and what that really translates into on a signaling level. I only really know a little about how to do that in memory-mapped IO systems like the Commodores (and to be honest I don't understand how the buses work there, just how to poke and peek.) Thanks! -- Eric Christopherson

7 years, 1 month

Powering Sun 3/60 without a chassis was Re: Sun 3/50 processor board and unknown processor

by chd＠chdickman.com

On Tue, Nov 21, 2017 at 1:51 AM, Mattis Lind <mattislind at gmail.com> wrote: > I think this is a 3/60 processor. Not 3/50. I said 3/50 because that is what the silkscreen says. I found some picture online and the 3/50 was a different layout. It sure looks like a 3/60 Looking at some online schematics it looks like the P3 96 pin DIN connector may only be for power. Is it possible to power this thing through that connector without a proper chassis? I know nothing about Sun hardware. -chuck

7 years, 1 month

LA30 parts and question

by fritzm＠fritzm.org

Hi folks, I'm picking my way through an LA30 restoration right now. It was pretty filthy, so I've needed to pretty thoroughly disassemble it for proper cleaning. I noticed that a few of the thin steel ribbon springs in the paper path are missing or broken on my unit, and some of the rubber bushings have hardened and deteriorated. Long shot ask, but wondering if anybody out there has spares of: 74-08648 (Spring, paper drag) 12-10357-3 (Bushing, rubber mount) 12-10358-3 (Ring, rubber mount) Also, the maintenance manual recommends Molykote B2KR for lubrication in a few places, but I can't seem to find specs on what this was. Can anybody recommend an equivalent modern alternative grease? cheers, --FritzM.

7 years, 1 month

LA30 parts and question

by jnc＠mercury.lcs.mit.edu

> From: Fritz Mueller > Overall, I have been pretty amazed by the sheer number of machined > parts, castings, high quality bearings, etc. within this beast. Lots of > stainless steel throughout. Sure wouldn't find anything built this way > these days! What a tank. That's DEC for you - quality engineering (mostly :-). Reminds me of this Porsche/Lotus story: http://www.chiappa.net/~jnc/nontech/chapman.html Alas, that kind of engineering turned into a liability when DEC tried to compete in the 'new world' of personal computers... :-( Noel

7 years, 1 month

Signetics TWIN

by cc＠informatik.uni-stuttgart.de

Hi, do hardware manuals for the TWIN exist? And does any other TWIN system exist? It seems it is a completely forgotten and lost development system. Christian

7 years, 1 month

Ideas for a simple, but somewhat extendable computer bus

by jnc＠mercury.lcs.mit.edu

> From: Charles Anthony > a hybrid PDP-11 (16 bits) / PDP-15 (18 bits) on a shared bus (UNIBUS?) That's a UNICHANNEL-15: it allowed devices on the -11 to do DMA directly into the PDP-15's memory through the MX15-B Memory Multiplexer. Odd factoid: this UNIBUS could run in 18-bit mode (!!), where the UNIBUS' two parity lines were recycled into 2 extra data lines. Some DMA interfaces (e.g. the RK11) could support this; in this particular case, it allowed the PDP-15 to use RK05 drives. Noel

7 years, 1 month

Idle question: Color of tape coatings

by cclist＠sydex.com

While working on some old (again!) half-inch tapes, I note that some of the very old ones have an oxide coating about the color of milk chocolate. Newer ones are anywhere from dark chocolate to black. Reel construction is another aspect. The really old ones tend to be all clear plastic, including the hub area. Newer ones have either a black plastic reinforcement to the hub or employ an aluminum sleeve. In most cases, the oldest of these is from around 1964, but probably older than that, as the only clues I have are dates placed by the tape librarian when a tape is put back into the pool or a label indicating when the tape was last recertified. Was there a date after which *all* half-inch tape became the dark brown to nearly black in color? --Chuck

7 years, 1 month

Sync on Green RGB video

by dj.taylor4＠comcast.net

I have a couple of vaxes that output 'unique' video, Alpha 3000 300, Alpha 3000 400, Vax 4000 VLC, and Vax Station 3100 M76. The Alpha and VLC each have a 3W3 type of connector and the 3100 has a 15 pin DEC designed connector. What does it take to connect these to inexpensive, modern VGA light weight monitors? Doug

7 years, 1 month

Ideas for a simple, but somewhat extendable computer bus

by spacewar＠gmail.com

On Nov 20, 2017 7:41 AM, "Tapley, Mark via cctalk" <cctalk at classiccmp.org> wrote: Catching up late, sorry if this is an old question, but what did the Digital Group computers use? My recollection is that they offered cards with 6800, 6502, 8080, and Z-80 CPUs on the same bus, and that part of the system seemed to work reasonably well. The Digital Group had two separate buses, a memory bys and an I/O bus, as well as two other slot types incompatible with either bus, for a CPU card and a TVC (video and cassette) card. They didn't support interrupts or DMA on any bus. If you wanted to use an interrupt, you had to wire it over the top. Doc Suding said that he didn't put interrupts on the bus because (paraphrasing) they are complicated and you don't need them. As you say, they did support various CPUs, but not more than one in a system. I wouldn't recommend that anyone consider The Digital Group as an example of good bus design.

7 years, 1 month

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test-drb November 2017