test-drb October 2010

test-drb@ccmp.vtda.org

175 participants
274 discussions

Single-board TTL PDP-8 (was Re: pdp-8/i ECO history?)

by ethan.dicks＠gmail.com

On 10/20/10, Vincent Slyngstad <vrs at msn.com> wrote: > From: "Ethan Dicks": Wednesday, October 20, 2010 8:14 AM >> On 10/20/10, Vincent Slyngstad <vrs at msn.com> wrote: >>> Hmm. I might choose the 8/L for something like that. Possibly soup >>> up the memory to 32K, but leave out all the option cruft of the 8/I >>> backplane. >> >> And replace the 7453 and 7482 with something made with less unobtanium? > > Sure. We've talked about how to do that before, I think. You'd face that > problem starting from either the 8/I or the 8/L. Yes, but I thought it worth keeping in play. >> The memory extension hardware to take it over 4K is obviously >> non-trivial in size (especially considering it doesn't fit in an -8/L >> CPU enclosure). > > Good point. You would definitely need some board area for that. Considering how much of the -8/i backplane it takes up (about 1/2 as much as the EAE), it's a noticable chunk. >> OTOH, if you have over 32K (*have over 4K) >> there might as well be provisions for OS/8-compatible mass >> storage, otherwise it's just a papertape machine with more than 4K. > > True, though an RF08 emulation doesn't take much board space. Nope. That takes about 3"x5" in TTL (with a 16-bit Dallas RAM/battery module), IIRC. > Or one could go with an RX08 interface for extra clanking ambiance :-). While amusing and handy for some (I would use it), unless someone whips up a cable-compatible RX01/RX02 emulator (could be to floppy or removable FLASH), there are only so many original drive sets running around. Of course, one could build that RX01 emulator and include an optional Arduino-based MP3 player to emit the whirring and clanking. Frivolous but entertaining. -ethan

13 years, 8 months

More on Alto repair

by mark.kahrs＠gmail.com

Once, after doing something stupid (I'm not sayin'), I had a killed Alto on my hands. To find the bug, I put a Biomation logic analyzer on the backplane microcode address bits. Using a listing of the microcode I was able to figure out which task was running when and that pointed out the loop in the microcode. I was then able to work backward from the task logic to figure the bug. This is made possible because the Alto backplane was wirewrapped, which meant that the signals are available for easy probing (and logic analyzer pins). Once upon a time I used to say "What I wouldn't give to have an Alto again". Now, I know it's not $30,100.

13 years, 8 months

Preserving computers (here we go again)

by wdonzelli＠gmail.com

>?I > believe that preserving classic computers is VERY different from > preserving many other types of collectibles. For those of us that have been around from the very beginnings of the computer collecting (which seems to be perhaps 1990 or so), or better for those of use that have been around from before anyone gave a damn, we see that it has grown up almost perfectly in line with how every other branch of the antique and collectible trade has. 1) A few see potential in some unrealized common items. 2) Very loose communities form, and collection form. 3) Snowball effect of more people see the potential and interest grows. 4) Prices and values start forming, due to supply and demand. Meanwhile, the good stuff starts getting scarce, 5) Markets grow, prices stabilize. The high end gets very high, and the low end gets worthless. You name the antique, and it will fit this story. Oddly enough, Ebay probably has not changed the story much. -- Will

13 years, 8 months

pdp-8/i ECO history?

by v.slyngstad＠frontier.com

Does anyone have the ECO history of the pdp-8/i available? I am looking at http://www.bitsavers.org/pdf/dec/pdp8/pdp8i/PDP8-I_CPU_blueprints_1969.pdf. On sheet d-bs-8i-0-6 there's a gate added at D6 in the drawing, probably in ECO #13, #25, or #50. It uses the M113 at F32N2 to invert something called "IO PC LOAD", and connects to a previously tied high input of the 4-input NAND at E32E2 (which calculates "PC LOAD"). The problem is, nothing anywhere in the drawings appears to generate a signal called "IO PC LOAD". I don't imagine anyone knows off the top of their head what this signal is, how it is generated. A look at the ECO history should help explain when this was added and why, though. Also, if anyone knows of an I/O device or option for the 8/i that would load a new value into the PC, that might give some clues where to look. Thanks in advance, Vince (I am making excellent headway on a project which translate the 8/i schematics, including all the options, into Verilog for an FPGA, but I currently have this signal tied to an input pin for lack of any information about it.) -- o< The ASCII Ribbon Campaign Against HTML Email!

13 years, 8 months

Oldest original proper computer (stored program etc)

by roger.holmes＠microspot.co.uk

I have looked it up again and what I was referring to was CSIRAC, in Melbourne. > > Is your 1301 older than TNMoC's Elliot 803? I'm pretty sure that's 1962, too, > but I'm not sure which month... The 803 is another project of the Computer Conservation Society and the chap who told me my machine was the oldest (Rod Brown) had just come back from a committee meeting of the CCS, so I presume they think mine is older but I would not like to argue that point, I was only nine years old myself in 1962. I know my 1301 was installed in time for program development to be finalised before it went live to handle the University of London's undergraduate matriculation in 1962. The reason the University got a prototype machine was that they threatened to tell the world there would not be any new undergraduates in 1962 and that a company called ICT was responsible. A machine destined for internal software development was quickly diverted to the university. Every few weeks a team of engineers would take over the machine for few hours and implement the changes made to all the other six prototypes at GEC telephones Coventry and ICT Putney and maybe elsewhere too. I am not interested in machines which have not been powered up for more than a year, even if they were operational when stored, the likelihood of them working when turned on again is low. Expansion and contraction, static electricity, chemical reactions especially in old electrolytic capacitors take their toll. Computers were built to be used, one which cannot be operated is no more interest to me than the hull of an old ship. I love the wonder of small children when they see how big, heavy, noisy and yes, smelly old computers used to be than the modern things they are used to. I love getting them to type their name on a Teletype, feeding the tape into the computer and have it print their name in legible tape (aka ClearWrite). Later on I hope to have it print their name on the 600lpm line printer, maybe in some fancy way with big letters made of lots of small letters or some such. Next year I might make it punch a legible card as that now works once more. Thanks for your thoughts. Roger.

13 years, 8 months

P112 good news

by dgriffi＠cs.csubak.edu

As many of you have already know, I've cancelled the new run of P112s and am in the process of issuing refunds to all who put money down. This takes a while. The good news is that Professor Feedlebom recently discovered at least six populated boards left over from the last run. Our intent is to gather the leftover parts from the last run and assemble kit bags. They will be offered to those who placed preorders in chronological order -- one kit per customer -- until people on that list have had a shot. I'll know more about how many kits will be available when Feedle takes a trip to his storage unit on Thursday -- David Griffith dgriffi at cs.csubak.edu A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail?

13 years, 8 months

Triage I - PROM Programmers & 5400s

by technobug＠comcast.net

I'm in the midst of chipping away at "The Pile" and offer the following to the list prior to supporting Witman's campaign or skipping them: Two PROM programmers: US$ 10 each + shipping - See: <http://elipsoid.home.comcast.net/~elipsoid/PROMPrgmrs/index.html> Data I/O Model 20B MOS Memory Programmer. I have no info on the beast, but appears to program the following: 2704 2732 764N 2708 732A 2764 2716 7320 8741 2508 7321 8748 2516 8764 8749 4816 2564 8755 2532 SPI Model 8407. PROMs are listed on the pull-out card pictured. Again no info available. I also have five bundles of ~300 14-pin ceramic ICs that test out as 5400/7400 TTL. Assume that they are 5400s since they came from a Hughes Aircrash auction many years ago. Available for postage. Shipping from 85704 - USA CRC

13 years, 8 months

PDP-8/L lamps

by jdr_use＠bluewin.ch

So where would I get exact equivalents for the 8-L bulbs these days ? around 10 pcs needed..... Jos

13 years, 8 months

Mac Classic near death... or at least an OOBE...

by zmerch-cctalk＠30below.com

So, there's a Mac Classic that was dropped off at my friends' store (otherwise headed for the skip/dumpster) and I "rescued" it. Yes, I used quotes, as there was this "weird" bright yellow and purple goo emanating >from the unit. Thinking something completely odd was spilled *into* the unit, I took it apart to find the damage. Turns out, the PRAM battery was in such bad shape that it was the source of both the purple (rust & other dissolved metals) and yellow (still not sure what that is) goo. I had to pry the motherboard out of the unit (slightly destructively) due to the corrosion on the rails on one side of the motherboard rails just to remove the motherboard. Whatever was bent can be unbent, but will need a *lot* of cleaning to refurbish. The contacts for the PRAM battery were completely gone on the (+) side, and gosh-darned near gone on the (-) side (enough so that it couldn't be repaired). I removed the PRAM battery & holder (with a pair of pliers as it was also damaged to an unrepairable state). That said, what do I actually do with the thing? My idea: Disassemble the unit and turn it into a 68K "microcontroller" trainer unit with a recent(ish) Flash ROM and Static RAM. Yes, I have the technology to build that. Or... back to the original destination (bad). Anyone want it for price of shipping? And yes, for those "keeping score" I have now built a "Mac Cracker." Do I get a prize for being the "Last Geek Ever" to build one? ;-) Laterz, "Merch"

13 years, 8 months

More SCSI Confusion

by robert.jarratt＠ntlworld.com

Right now I have two disks and one CD-ROM in my Alpha 433au (all attached to the internal ribbon cable, if you have seen my question about the storage shelf, that is not connected in this instance). The SRM recognises them correctly thus: dka0.0.0.1009.0 DKA0 COMPAQ ST32550W 6415 dka400.4.0.1009.0 DKA400 MATSHITA CD-ROM CR-508 XS03 dka600.6.0.1009.0 DKA600 IBM-PSG DDYS-T18350N M S96E However, when I start the Debian installer, during the boot sequence it does a SCSI reset and then only recognises the first disk, thus: scsi(0:0): Resetting SCSI BUS scsi0 : QLogic QLA1040 PCI to SCSI Host Adapter Firmware version: 7.65.06, Driver version 3.26 Vendor: COMPAQ Model: ST32550W Rev: 6415 Type: Direct-Access ANSI SCSI revision: 02 So, for whatever reason, the CD-ROM and the other hard disk disappear. I have checked the termination and it *seems* to be correct in that the disks and the CD-ROM are not (or *should* not) terminating anything. There is a terminator at the end of the SCSI cable, and I believe the QLA1040 SCSI adapter does its own termination: >>>sh pk* pka0_host_id 7 pka0_mode ultra pka0_soft_term diff Does anyone have any suggestions why the SCSI reset during boot should make the CD-ROM and the other HDD disappear? Thanks Rob

13 years, 8 months

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test-drb October 2010