Noel Chiappa jnc at mercury.lcs.mit.edu
Thu Jun 2 13:19:04 CDT 2016

    > From: Rod Smallwood

    > Needless to say all of the locations I examined came up filled with
    > zeros.

Device registers will be in the range 17760000-17777776 (although toward the
top you'd mostly see CPU registers). The RX02 controller (RX211) should be at

    > Although the monitor display says Unibus system. I suspect what I have
    > is a CPU used in a Qbus system with a hacked monitor and boot eprom.

Hmm. Well, the same physical board should work in either system (/93 or /94)
- and I suspect the ROMs check to see if there's a UNIBUS adapter (KTJ11)
there, and declaim the CPU board as a UNIBUS or QBUS, depending. (I.e. I
would wonder if there are separate QBUS and UNIBUS ROMs.)

That's because I have this bit set that there aren't separate /83 and /84
versions of the KDJ11-B for the two busses, and I would think that the /93
and /94 would likely be the same. (I should read the -B and -E manuals to
confirm that.) And I don't think there are separate part numbers for
KDJ11-E's for QBUS (/93) and UNIBUS (/94) systems.

But I'm not familiar with the ROM contents, so I can't say for sure. When
debugging broken hardware, I tend to ignore boot/diagnostic ROMs anyway, and
stick to simply what the hardware does (as seen via ODT), as that's a) much
less complex, and b) fully documented. (I don't know of any ROM listings, and
I'm not about to disassemble them!)

So if you can't see the RX211 registers from ODT, let me know, and we'll
figure out what to try to see if the KTJ11 is working properly.

    > For whatever reason they managed to disable the unibus  I/O

I'm not sure you can (in hardware terms, that is - and clearly if there's no
way to do it in the hardware, the software cannot do so)... although it could
be broken.

    > I have what I believed is a working 11/83 in my computer room
    > I'm going to try my processor in there

There's a section in the /94 maintainence manual (EK-PDP94-MG-001, available
online) about upgrading an -11/84 to an -11/94; you might want to read that
to see if there are any gothca's in terms of the cabling, etc. (The console
cabling will be an issue, of course, since the KDJ11-B and KDJ11-E use
different console connectors on the board - I'm talking about the other

But AFAIK the KDJ11-E (/93 and /94) is a compatible upgrade to the KDJ11-B
(/83 and /84), so your plan should work.


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