PDP-11/23 Debugging

Ben Sinclair bensinc at gmail.com
Wed Nov 19 08:56:18 CST 2014

Thanks a lot for your help Noel!

I did write a Ruby program to enter programs in from files via ODT, so I
can probably run your test that way, assuming it's a set of addresses and

I agree that it's unlikely both of my CPU boards are bad in the exact same
way, so hopefully I'm on my way to figuring it out!

That PDF is the one I was looking at, though it looks like there are more
diagnostics available for the 23+, so that might not be completely
equivalent to the test available for the 23.

I'm hoping a memory test shows that I have some problems there, which is
potentially the easiest thing to fix. Someone told me a while back that the
M8044 memory tends to be fail, so maybe I should look for something else. I
wouldn't mind having more memory anyway!

On Wed, Nov 19, 2014 at 8:33 AM, Noel Chiappa <jnc at mercury.lcs.mit.edu>

>     > From: Ben Sinclair
>     >> Is there a DL11 diag you can run on it? (If not, I can whip up a
>     >> simple test to check it out.)
>     > The diagnostics manual mentions this:
>     > But, the only XXDP disks I have are the ones from AK6DN, and that
> test
>     > doesn't appear to be on any of them.
> OK. Give me day or so, and I can whip up a really small test that you can
> toggle in to check out the interrupt on the console line.
> I won't be able to give it to you in a down-loadable format, alas: I'm
> working with a Unix (V6) toolkit, and at the moment I don't have the
> ability
> to produce DEC-format binary files, just Unix a.out.
> At MIT we did have a complete set of things for V6 Unix for doing
> DEC-compatible stuff (MACRO, LINKER, along with programs to convert back
> and
> forth between .REL and a.out format, and also to convert things to .LDA
> format), but at the moment the backup tapes I have which contain all that
> are
> in the process of being read, so there's no point to re-writing them all.
>     > I've run a memory test program I found that's not part of XXDP, and I
>     > believe it's fine, but is there a test in XXDP I could run?
> Sorry, I don't know anything about XXDP. Maybe someone else knows?
>     > I don't see anything in the XXDP manual related to an M8044/MSV11.
> I'm not sure they'd have a MSV11-D-specific test program; it has no control
> registers or anything, so just a generic memory test is all you can do
> with it.
>     > I moved all of the jumpers from my old M8186 to the new M8186. It
> works
>     > just the same... It still fails that CPU test.
> So it's not a CPU problem. Starting to sound like maybe a DLV11-J problem
> - or
> maybe the test wants something we don't know about?
>     > I found the microfiche for the KDF-11B on Bitsavers, but they're
>     > missing the one for the KDF-11A unfortunately!
> That might still be useful. I wanted to look at the -11B one, but I'm not
> sure I've found it; is this it:
>   www.bitsavers.org/pdf/dec/pdp11/xxdp/fiche_200dpi/0170_CJKDJB0_1123B.pdf
> The KDF-11A and KDF-11B are _almost_ identical, programming-wise (they use
> the
> same chip-set) - the only differences I know of are that the -B has i) a
> built
> in LTC register, and ii) Bootstrap and Diagnostic registers.
>     > I wish I had the microfiche for this CPU, as the one for the KDF-11B
>     > lists the hardware requirements!
> Looking at that CJKDJB0_1123B thing, it does seem to want things specific
> to the -11B (e.g. it tries to test the second on-board serial line).
> If it's not a simple DLV11-J problem, I see dis-assembly in our future,
> sigh.
>         Noel

Ben Sinclair
ben at bensinclair.com

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