multiple cpu machines Re: rogues galleries

dwight elvey dkelvey at
Tue Nov 28 23:55:21 CST 2006

>From: Jules Richardson <julesrichardsonuk at>
>Chris M wrote:
>[Dimension 68000]
>>  Was curious if there was anything like it across the
>>pond. Or did I ask this already...
>Closest thing is probably the humble BBC micro, to be honest. Acorn 
>designed them from the outset to allow add-on processors to be used 
>(externally on the model B, and either externally or internally with the 
>later Master series), and for the second processor to be able to take over 
>control of the host BBC. They always had plans for Z80 and additional 6502 
>boards for the machines; I believe that the 32016 and 80186 boards weren't 
>envisaged until later on.
>Several manufacturers (including Acorn) made coprocessor boards for the 
>machines (notional OS in brackets, although you were free to run what you 
>wanted really):
>Acorn Z80 (CP/M)
>Acorn 6502 (application-level code)
>Acorn 65C102 (application-level code)
>Acorn 32016  (Master internal, PanOS)
>Acorn 32016 (1MB variant, PanOS)
>Acorn 32016 (4MB variant, PanOS)
>Acorn 80186 (DOS)
>Acorn 80286 (DOS)
>Acorn ARM1 (Brazil monitor only)
>Acorn A500 (Arthur. Not to be confused with the A500 distinct machine)
>Casper 68000 (FLEX / program development)
>Cumana 68008 (OS-9)
>PEDL Z80 (unknown)
>Torch Z80  (CP/N)
>Torch 8086 (DOS)
>Torch 68000 / Z80 combo (UNIX and CP/N)

Olivetti M20 8086 (DOS or CP/M86) ( has Z8001 as main processor )

>Two versions of the Torch 68k board existed - the later one was faster and 
>with more on-board memory. Two versions of their Z80-only board existed 
>too; one had a local serial interface.
>People have privately homebrewed other CPUs for the system (6509, 6809, 
>ARM7 and PDP-11 spring to mind).
>However, whether all this 'counts' or not is debatable; Acorn didn't 
>(sadly) forsee people wanting to have more than one 'secondary' CPU 
>attached at any one time, so the connection between the BBC side and any 
>additional CPU was really point-to-point only rather than a true bus; I 
>think Torch were the only people to offer a setup that contained both 68k 
>and Z80 alongside the BBC's native CPU (I seem to recall that in their case 
>the switch between CPUs is handled by on-board firmware and a bit of 

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