[Rpcemu] Thoughts on RPCemu development

Ed Avis eda at waniasset.com
Fri Aug 31 19:59:47 BST 2007

Tom Walker wrote:

>>May I suggest going backwards and adding support 
>>for emulating an A5000-ish computer?

>I did put together such an emulator a while ago. It's not been 
>released as it's a bit unstable (only boots RISC OS about 1 in 
>3 times), buggy, and not actually that fast (about 50% faster 
>than RedSquirrel, considerably behind VA5000/VARPC and 

I don't know how fast Red Squirrel runs compared to arcem - I should download it and run some simple benchmarks.

(arcem is often faster than a real Archimedes, although under X11 at least the mouse pointer can be jerky.  I started playing with ways to improve that, such as letting the X11 mouse pointer move freely and then generating mickeys artifically to move the RISC OS pointer to the correct position, but so far I haven't got anything usable.  If there is any clever trick you use in Arculator / RPCemu I'd be interested.  End digression.)

>The only unique feature I'm aware of, is that it could emulate 
>a high res mono monitor (1152x896),


As you say, this is not so useful because under emulation you can just create an ordinary screen mode of the size and pixel depth you want - no need to tell RISC OS that it has monitor type 2 or whatever it is.  (I am looking for a way to generate custom screen modes without having to fiddle with assembler and register settings each time - do you guys know of a good free utility that lets you type in the resolution and colour depth?)  (Also I know that the Computer Concepts ColourCard introduced 256-colour screen modes with a 256-colour palette, and patched RISC OS to use them.  Does anyone know the technique used?  It should be pretty simple to extend arcem to support more palette registers.)

>RISC OS 3.1 was widely available when I first discovered 
>Archimedes emulation (2001), but there was a crackdown a few 
>years ago and it's quite difficult to find.

It's still there, as is RISC OS 2... a shame that even the older versions aren't officially legitimate.  Even the BBC Micro ROM images are still under a cloud I believe (indeed it's not even clear who owns the copyright these days).

I'd love to get hold of Impulse from CC, but nobody seems to have a copy.  It would have the distinction of being even more useless than Arthur.

>>get ARM Linux running

>Actually, this is more difficult than you might think. It's 
>easier to start again emulating a new machine, than tracking 
>down obscure bugs in an existing emulator (which is why RPCemu 
>doesn't run ARM Linux as of yet).

I see.  Yes, Linux does tend to work the machine a bit harder than RISC OS.  NetBSD would be worth a try - but that might not work either.  Um, ARM Minix?  Whatever ;-p.

Ed Avis <eda at waniasset.com>

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