Date   : Sat, 21 Sep 2013 12:04:08 +0100
From   : bbc@... (Dave Curran)
Subject: Early BBC MOS EPROMs

Thanks for the info. As I say I'll give that a go on an older board if I
get a chance. I thought this might have been 'pre-release' from when api's
would still up for change, rather than released code, where as you say,
they shouldn't be changed.

Looking through the other roms that came with this set with a little more
interest now. Most were blank and have been reused. The ones that were
labelled up I kept. Most are standard stuff. There's one marked Hi BASIC 1
and a set of Arthur 1.1 and RISC OS 2.01. There's also one marked 'satpic'
which shows version 2.0 (c) 1984 By Matthew Atkinson and Peter Clappison?

Thanks,

Dave


On 20 September 2013 17:45, J.G.Harston <jgh@...> wrote:

> Dave Curran wrote:
> > Ah yes, my combined image matches the MOS 010 image on mdfs.net [5].
> > That's answered that question.
> > Not sure why it doesn't work though. Next time I dig out my issue 3
> > model A, I'll see if it works on there.
>
> The entry points and functionality are the same, that's the whole point
> of an API. The significant difference between OS 0.xx and OS 1.xx is that
> the keyboard handling in OS 0.xx is different and has been described as
> only working "by accident". The OS 1.xx keyboard handler was rewritten, and
> later hardware is slightly different sufficiently that the OS 0.xx keyboard
> handler can't cope with the later hardware. That will be why you end up with
> no keyboard input.
>
> On the point of the MOS entries, there are some slight differences.
>
> There is an entry to FSCV at &FFCB.
>
> OSARGS appears to support calls with A=4 to 7.
>
> *CAT calls OSBYTE 138,<drive> which, if CFS is not selected passes the
> string "CAT" to FSCV.
>
> OSBYTE 123 enters the current BRK handler.
>
> There's a *DEBUG command, a *NOTAPE command that disables filing system
> access, and *DISK and *DISC commands - in the MOS.
>
> The VDU drivers, the MOS kernel and the CFS filing system are more
> rigoursly segregated in the ROM, with each code block starting with an
> entry jump block.
>
> There's a different definition of sideways ROMs. The MOS builds a table
> of ROMs 3, 2, 1 and 0. If a ROM's flag has bit 7 set, then it is called at
> &8000 (yes, the language entry) on startup. Then the highest ROM with
> bit 6 set is entered either at &8000 if bit 1 is clear or at &8003 if bit 1
> is set. It would be interesting to find a sideways ROM written for OS 0.xx.
>
> --
> J.G.Harston - jgh@... - mdfs.net
>
>
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