Path: utzoo!utgpu!cunews!bnrgate!uunet!mcsun!ukc!axion!tharr!gtoal
From: gtoal@tharr.UUCP (Graham Toal)
Newsgroups: comp.sys.acorn,eunet.micro.acorn
Subject: Re: BBC micro + the 6809 (was: MODE-21 ...)
Message-ID: <1585@tharr.UUCP>
Date: 9 Jan 91 01:28:06 GMT
References: <3802@aipna.ed.ac.uk>
Reply-To: gtoal@tharr.UUCP (Graham Toal)
Followup-To: comp.sys.acorn
Organization: Power Microsystems Ltd
Lines: 29

>> (GWP - Gods Wonderful Processor)
>
>Wasn't it just - think how nice stuff like paged ROMs etc could have worked
>with a changeable base page and 16 bit indexed modes.  I daren't think of
>a system with OS/9 and the 6809 MMU.  I guess after they spent all
>the board real estate on speech processors, teletext support,
>silly tube connector etc, there wasn't much budget left for the CPU.

Actually I built a 6809 2nd processor while I was working at acorn -- rather
neat though i say so myself -- it was a 4 package tiny board -- custom ram
address decoder/refresher, rom, 64Kram sil & cpu.  I was hacking VLSI at the
time and it was for a test chip (it worked), but I never got as far as putting
any real software on it.  It would have gone fast enough for tube operation
using the FIQ and NMI intrrupts slightly differently from the obvious way
Acorn considered when they looked at it and said it was too slow :-)

Actually I was a bit depressed by it, because to prototype the software I 
wrote a 6809 emulator for the 32016 Panos machine... and it ran faster
than the real chip :-(  Motorola never put the hardware engineers onto
speeding it up beyond 2Mhz unlike the Z80 or 6502 rivals.  Probably because
it had been designed by software people in the first place :)

I still have it by the way, if any real fanatic is serious about getting
it running.  You'd have to know the tube code inside out and know a lot of
electronics to do a bit of necessary circuit redesign.

Graham
-- 
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