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

Noel Chiappa jnc at mercury.lcs.mit.edu
Sat Nov 23 09:48:53 CST 2019

    > From: Jörg Hoppe

    > UniBone can be used in UNIBUS-A SPC slots in 18 bit mode without any
    > extra adapters? And can emulate an RH11-C there

As far as I can see, yes.

    > even if the RH11 is supposed to run in UNIBUS B?

Well, all RH11's have both UNIBUS A and UNIBUS B; under program control, one
can select either A or B to be the one where the DMA from the RH11 happens.
(Access to the registers in the RH11 is only possible via UNIBUS A, and
interrupts from it can only happen on A.) I'm not sure exactly what your
question is, but I hope that answers it! :-)

    > We've seen early SPC slots (PDP-11/40, '45) without NPG wired,
    > 'cause SPC was apparently originally meant for "Small" peripherals
    > without DMA. Is KS10 UNIBUS-A wired to be DMA capable?

Good question! Well, the RH11 is designed so that it can other devices
'downstream' from it, on both UNIBI. So that says that NPG is sent _through_
the RH11 on both UNIBI - but doesn't speak to the SPC slots. For that, one
needs to look at the backplane wire list - which isn't in the drawings! :-(
However, I happen to have an RH11-AB backplane, and it has the AA1-AB2 jumpers
for NPG on those three slots.

Same thing for interrupts - both UNIBI are wired to for them (although the
grant lines for UNIBUS B don't go into the RH11 cards, they are only on
the RH11 backplane).


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