Date   : Wed, 24 Sep 2008 00:54:12 +0100
From   : jgh@... (Jonathan Graham Harston)
Subject: Model A OS question.

Phill Harvey-Smith wrote:
> Anyway I have also found that I have an original OS 0.1 romset, and I
> wonder if it would make the A more authentic to fit these ? the Model A
> has an issue 3 motherboard and the OS and Basic roms are both mask
> programmed, though a *FX0 claims it's an EPROM :)
 
The only difference between a model A and a model B is the
hardware, not the firmware. Either model could have OS 0.10, OS
1.00, OS 1.20, BASIC 1, BASIC 2, and the MOS could be in a single
16K ROM or four 4K ROMs.
 
It would be a useful system to have for playing with to see what it
does. I've been meaning to plug MOS 0.10 into one of my Beebs and
see what it does. A cursory look through the code throws up some
interesting titbits. There's some assembly comments embedded within
it, messages include "System 3 loader", "No IRQ", "Bad event", "No
filing system"; *commands include *DEBUG, *DISK, *DISC, *NOTAPE;
there's no sideways ROM support and no extended jump block at
&FF00; there's a jump block entry to FSCV!
 
When I've commented it a bit more, I'll upload the source.
 
-- 
J.G.Harston - jgh@...                - mdfs.net/User/JGH
05:10:36, 18-Nov-2008 - RISC OS time rolls over to &5000000000