Do-It-Yourself PDP-11 help!

From: Vintage Computer Festival <>
Date: Wed Feb 16 07:48:22 2005

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

> OK, the Baydel card has termination resistors on it - does that mean it
> needs to go last in the chain?


> Looking at my backplane it appears that it is serpentine, rather than
> Q22/CD if I understand the documentation correctly - ie. AN2 on row 1
> goes to CM2, then CN2 goes to CM2 on row two, and so on.

So make sure you put the card in the correct slot at the end of the chain

> > 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.
> OK, I have (looking at the handles)
> M8192 M8044
> (nothing) Baydel
> I have confirmed that the M8044 passes the bus grant stuff through, and
> that the backplane is sending the signals where I think it is.
> The SLU led *still* stays on. Yes, the power supplies are good.
> I did *once* get the following:
> 173026
> _at_
> from it.

Ooh! So something is working. I'm guessing that the CPU is strapped to
execute the onboard bootstrap and, not finding anything to execute (or no
drive installed), crashed.

Did you notice if D3 (and only D3) was on when you got the output that one

> > If you've got another card with a console port to try out then that might
> > be something to try.
> Haven't got one. Are they difficult/expensive to get hold of?

Shouldn't be if a local listmember has a good lot of Qbus cards to spare

But it looks like you've got some intermittent fault somewhere perhaps.
Are you sure your console cable is secure?

Sellam Ismail                                        Vintage Computer Festival
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Received on Wed Feb 16 2005 - 07:48:22 GMT

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