Date   : Tue, 26 Jul 2005 00:54:04 +0100
From   : jgh@... (Jonathan Graham Harston)
Subject: Re: ARM copros, speech cartridges, real

Jules Richardson <julesrichardsonuk@...> wrote:
> On Mon, 2005-07-25 at 22:29 +0100, BeebMaster wrote:
> > Multiple second processors /co-processors must have been a possibility
> > in the long distant past as the Master Reference Manual description for
the
> > *X command seems to hint this
> 
> Well I have a feeling that the Tube was designed to be a bus with
> multiple devices on it, but the reality was that it had trouble coping
 
The *X command suggests that this was supposed to be possible. *X
just writes to &FEE8 and then loops, effectively waiting for a
RESET. It would require something to respond to a write to &FEE8
and then pulse RESET down.
 
> alongside others on the same bus. Yet connecting both a 6502 and Z80
> copro to the same machine doesn't seem like that far-fetched a thing to
> expect people to want to do...
 
I seem to remember that the Acorn Business Computer has three
CoPros - 6520, Z80 and 8086 - that could be selected somehow. I
have a feeling it was probablyt through a multi-way switch on the
side of the case :)
 
-- 
J.G.Harston - jgh@...                - mdfs.net/User/JGH
HADFS System Resources - http://mdfs.net/Software/HADFS