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

Jörg Hoppe j_hoppe at t-online.de
Fri Nov 22 08:13:14 CST 2019

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>> Although, with the 3 SPC slots - although they are on UNIBUS A, and only
>> UNIBUS B has the 18-bit capability
> It is of course perfectly possible to run UNIBUS _A_ (where the SPC slots are)
> in 18-bit mode too - although the _RH11_ can't use it that way. But you won't
> be using the RH11 anyway, so who cares?
>Also, I took another look at the KS10 tech manual, and they do in fact use use
>an M9200 'thin' jumper (although it's mis-labelled "M9300" in the diagram -
>that diagram has a number of errors, including the "M8014" in the UNIBUS 'A'
>In slot - they must mean an M9014 [UNIBUS to 3 flat cables] instead) to link
>the two UNIBI together. Which answers the question of how the KS10 CPU gained
>access to UNIBUS A (where the device registers, interrupts, etc are) when it
>also had to be connected to UNIBUS B (for 18-bit data transfers).
>So I think all our questions are answerered (except for the -AB/-C difference
So I understand right:
UniBone can be used in UNIBUS-A SPC slots in 18 bit mode without any extra adapters?
And can emulate an RH11-C there, even if the RH11 is supposed to run in UNIBUS B?
Thats good news.

Two more things to check:
1. 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?

2. When doing 18bit on UNIBUS-A we put all kind of signal levels
on parity lines PA,PB = DATA<16:17>.
Won't the KS10 CPU interpret these as real BUS parity errors generated
by some UNIBUS-A device?

best regards


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