Do-It-Yourself PDP-11 help!

From: Vintage Computer Festival <>
Date: Tue Feb 15 20:07:50 2005

On Wed, 16 Feb 2005, Gordon JC Pearce wrote:

> It *was* working but someone has removed the cards, and now I don't know
> which order they go in the slots. Perhaps if someone looks over what I
> have they can give me a bit of advice.

Ok, I'll use my newly acquired PDP-11 skills to attempt to help you :)

> I have (plugged into the machine when I got it):
> a KDJ-11A - I believe this goes in the top-left space, looking down into
> the sockets
> a Baydel B01076 card, with a couple of eproms, a console port, and a
> lead that goes to the front panel (more of which anon)
> a Fourth Generation Systems memory board, with 18 41256s on it (512kwords?)
> an RXV21
> an RLV12
> an SCD-DHV11 board
> the backplane is labelled "General Robotics Corp", and "P/N 027-0003-OC"

So far, so good. You pretty much have everything you need for a nice
system, and it looks like they're in order.

> a couple of other boards that weren't in the machine, which are:
> a WDC11-C board
> an M8044 memory board, 32Kx18 bit

You can leave those out for now. The WDC-11 just came up on the list
earlier today (or yesterday) and is an MFM hard disk controller.

> When I power the machine up, three of the diagnostic LEDs on the KDJ11-A
> come on, then go off after about 1/2 a second, leaving just D3 on -
> which appears to mean that it can't communicate with the SLU. Now, I'm
> guessing that means it can't see the serial console, which I believe is
> on the Baydel card.

> Do the cards need to go into specific slots on the backplane? If I

The CPU should go first. And depending on interrupt requirements, some
boards may need to be closer to the CPU than others. But I think your
current configuration is fine.

> google for anything in this machine I get lots of sites offering to sell
> me cards, but very little in the way of real information.

And you probably won't. It sounds like a generic system someone cobbled
together (not uncommon...I have several like this).

I'd remove the DHV-11 to simplify things. In fact, I'd remove all but the
CPU, Baydel, and memory cards, and troubleshoot with that.

In case you need some (or haven't found this yet) here's a good bit of
documentation on the KDJ-11A:

And as you already found out, D3 on indicates:

D3 Module attempted to read location 17 777 560 and timed out.
        Indicates SLU is not responding.

If you've got another card with a console port to try out then that might
be something to try.

Keep us posted!

Sellam Ismail                                        Vintage Computer Festival
International Man of Intrigue and Danger      
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Received on Tue Feb 15 2005 - 20:07:50 GMT

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