Date   : Mon, 09 Jul 2001 13:21:30 +0100
From   : Tom Seddon <T.W.Seddon@...>
Subject: Re: BEEB Stuff

>===== Original Message From "Peter Lloyd" 
<bbcmicro@...> ====
>> Has anyone developed or is thinking about developing BEEB games or BEEB
>> emulators (e.g. BBC Basic) for the Psion. I have a Psion 3a and I think
>> there was such a thing at one time as the 'Acorn Pocket Book'- has anybody
>> got one? Does this have BBC Basic.
>
>I've seen an Acorn Pocket Book - from sight it looks almost identical to a
>Psion 3a - just a few cosmetic differences. I also recall there being some
>technical differences - maybe with batteries, mains adaptors, or pc serial
>links, i'm not sure.
>
>In the 15 minutes I had to play around with it several years ago I don't
>remember that it did have BBC Basic - otherwise I'm sure it would stick in
>my mind and i'd have tried to get hold of one! I think it probably had OPL.
>

Indeed it did have OPL, rather than BBC BASIC.

I don't think a BBC emulator for the Psion 3A would be feasible. For a start, 
the processor is rather slow -- an 8MHz NEC V20/V30 (80x86 clone), which is 
really not fast enough for emulation with graphics at even a passable speed. A 
V30 doesn't even run MS-DOS at a decent speed :-)

(You would have on average 12 cycles for each 6502 instruction. I think the 
indirect jump for dispatching instructions would eat up all the time on its 
own.)

I think a very basic emulator which simulated OS calls in native code might 
run at a usable speed, but it would have to be written in assembly and 
debugging would be something of a nightmare -- if you screw up, _everything_ 
on the Psion might disappear...

Furthermore, the screen resolution (a more 480 x 160 if memory serves me 
right) would render most games unplayable, quite apart from the fact it's 
monochrome!

I presume you want the emulator for games... right?!?!

(The Psion 3 would be even worse, being half the speed and having one quarter 
the resolution.)

-- 
--Tom
+-----------------------+-----------------------------------------+
| T.W.Seddon@...        | My other life is 3rd person perspective |
+-----------------------+-----------------------------------------+