UniBone: Linux-to-DEC-UNIBUS-bridge, year #1

Noel Chiappa jnc at mercury.lcs.mit.edu
Thu Nov 21 17:33:03 CST 2019

    > From: Jörg Hoppe

    > did DEC construct 18bit mutants for a few PDP-11 peripherals to run
    > them in KS10?

Yes and no. There were two 18-bit UNIBUS devices, but they were originally
done for the PDP-15 (DEC's last 18-bit machine). They were the RK11-E and the
RH11-AB. When the KS10 appeared, the RH11 was re-purposed for it. 

(How the RH11-C in the KS20 differed I'm not sure. I know it used the
M7294-YA instead of the M7294, but I'm not sure how that differed. It's the
MASSBUS data buffer and control, so it's something MASSBUS related. The
RH11-AB already has the 18-bit stuff; see 4.16 "Logic Diagram DBCE", pg. 4-28
(65 of the PDF) in "RH11-AB Option Description" for details; it's poorly

    > From: Daniel Seagraves

    > There's still the problem of the disk Unibus itself to solve - the disk
    > UBA doesn't terminate into a normal Unibus. It goes into the disk RH11
    > directly, and the bus is terminated on the far end of the RH11. ... The
    > ideal scenario would be if the first slot of a RH11 (where the bus
    > jumper comes in) can accommodate the (quad card) Unibone without
    > issues, the rest of the RH11 boards can simply be pulled without
    > breaking bus continuity

The RH11-C seems like it's very similar to the RH11-AB, physically. Both the
'disk' and 'tape' RH11-C's seem like they are separate 9-slot system units,
with the same layout (in terms of boards->slots). Both have 3 Small
Peripheral Controller slots, like the -AB.

The first slot is purpose-wired to hold the M7296 and M7297:


so 'no' to that idea. Although, with the 3 SPC slots - although they are on
UNIBUS A, and only UNIBUS B has the 18-bit capability - although maybe the
two can be jumpered together (the way the two UNIBI in the KD11-A/D can).
(IIRC, the "RH11 Peripheral Controller Course" may talk about that.)

I don't think things will work with the RH11 boards pulled, unless you
manually jumper whatever pins are used to feed NPG and BG? through the
device. Probably the easiest thing is to change the bus address of the

    > From: Chris Zach

    > I seem to recall that the RH11C included a full length unibus slot
    > after the boards

Depends what you mean by "full-length"; no MUD (hex) slots, but yes to SPC
slots (SPC) - as above.


More information about the cctech mailing list