Next steps (was Re: pdp 8/e)

From: Chuck McManis <cmcmanis_at_mcmanis.com>
Date: Wed Oct 6 19:21:17 1999

>The two bad switches are yellow ones. The switch mechanism is there, its
>the paddle that is broken in one case, missing in the other. Though if I
>cant get yellow someplace, then any color is better than a non-operational
>computer...

Well, let me know. I've got a toasted 8/M front panel that I've used to
restore an 8/M and an 8/F. (one of the colors matches)

>And I just noticed that I actually have one usable [M8655] cable, though
it is very
>short. It runs from one of the serial boards, to just barely out side the
>back of the case, and it is labeled VT55. A white plastic connector, single
>line of connectors, and if i recall correctly, 6 wires connected. Some
>sort of current loop connector i'm assuming.

Yup, that would be the DEC "standard" three loop current loop interface.
(Tx loop, Rx loop, reader-run loop). You can get a compatible BERG
connector for the 8655 from Digi-key and build your own RS-232 cable. Check
out the schematics on Dave Gesswins(sp?) page.

>> Make up a positive bus interface and a DMA (data break) card.
>Which is nice. But what does this get me in the real world?

I believe they are required to support the DECTape interface but Eric Smith
would know for sure.

>Yep. Unfortunately I dont have any peripherals. Except the one RL01, and
>apparently I dont have an interface board for that.

I don't believe DEC made a Quad RL controller. I've only seen the M8433
which is a hex wide RL controller that plugs into the PDP-8/a. But you also
said you have the Omnibus expansion stuff, which means that if you get a
PDP-8/a backplane you can jumper over to it and install the RL controller
there...
 
>I've always wanted a PDP8/e. Always. Which is why I already had in my
>possession 2 complete 3 board sets of core memory, 8K per set, for the
>PDP8/e! And I bought another 8K plane on ebay this summer. these things
>tend to attract one another...

Bravo!

>I think I have enough [top connectors]. Not if I want to get a third set
>of core memory
>installed, but its a long shot that the third set will work anyways. At
>the very least the boards have to be tuned to work together, or some
>such magic incantation uttered.

Yes, I have just such a stack and its a bit daunting at the moment.

>Its standard pdp8/e lights as far as I know. Manufacture date is 1976.

Hmm, look at the front panel from the front, then look over the top and on
what is the left hand side, see if it has one power line hooked up or two.
If it is only one, there may be LEDs. I thought they didn't make any lamp
panels after '74 but I'd love to be proven wrong.
 
>One strange thing... The front panel doesnt say Maynard, Massachusettes, as
>I expected... it says something like Galway, Ireland. Oh my GOD, its
>the RARE Galway version! I can sell this on ebay and have more money
>than Bill Gates! er, aHem.. I'm much calmer now...

Now _that_ is fascinating. If you get a chance read the part number of the
panel off the back and post it. Also be _sure_ the power supply is looking
for 110V and not 220V!!

>Ok, so what do I need to obtain from here.. looks like I have the basics
>of a PDP8/e system with serial ports. High speed paper tape reader interface,
>but no paper tape reader... What would make this a minimal usable system?
>Just adding a TTY33, and getting someone to copy a few paper tapes, perhaps?
>If the core memory doesnt work out, is the MOS memory actually affordable?
>Anyone willing to tell me some PDP parts suppliers that may have some
>interface boards, like whatever I need to hook up that RL01 (what exactly
>is a RL01 anyways). Maybe I should be looking to add floppy drives, etc.
>OR, are people using IBM's as a terminal, and running some program that
>pretends to be an attached paper tape reader/punch unit? That might do
>for starters, though its not anywhere near as satisfying.

Step zero of course is restoring the line cord and power.

Step one then is to put together a minimal system (8330, 8300, 8310, 8655,
837, 849, Core stack, 8320 bus loads.) You can do some tests with just the
CPU cards in as well.

Step two would be to get RS-232 connectivity to a PC, toggle in the RIM
loader and load some the of the diagnostic tapes. In particular the memory
exerciser and the instruction set tests.
Received on Wed Oct 06 1999 - 19:21:17 BST