Unixlike, multitasking 6502 (was Re: Nuke Redmond!)

From: Cameron Kaiser <spectre_at_stockholm.ptloma.edu>
Date: Tue Jan 16 15:15:21 2001

> There are quite a number of multitasking 6502 machines out there.
> Homebrews and C64s are represented.

Yep, I've played with LUnix and OS/A65. Both fun but not really Unix.
LUnix NG does have one cool feature; it can do PPP out of the box on a stock

> Can you make a 6502-based machine 'do' virtual memory?

Not natively, which was why I wrote:

> at 03:31 PM, Cameron Kaiser <spectre_at_stockholm.ptloma.edu> said:
> >I run AIX and NetBSD myself! :-) And, one of these days when I get my
> >6502-on-6502 virtual CPU implementation done, my C64 will run my own
> >Unixy flavour too (just to make this on-topic somewhat).

... a virtual CPU implementation. Actually, what it would do is distill
instructions down to their absolute, immediate or implied addressing
counterparts (instead of zp-indexed, absolute indexed, indirect, etc.),
and then munge the address operands to point to the right memory block.
It would move stepwise through code like that, with things like branches
and stack manipulations being emulated operations. There is no good way,
short of one fancy piece of MMU logic, to do VM on the 6502 currently.
So, with the advent of fast CPUs for the C64 like the SCPU, why not do it
in software? :-) It would probably not run badly even on a stock system.

Ach, du lieber -- this thread is back on topic!

----------------------------- personal page: http://www.armory.com/~spectre/ --
 Cameron Kaiser, Point Loma Nazarene University * ckaiser_at_stockholm.ptloma.edu
-- Schizophrenia beats being lonely. ------------------------------------------
Received on Tue Jan 16 2001 - 15:15:21 GMT

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