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

From: THETechnoid_at_home.com <(THETechnoid_at_home.com)>
Date: Tue Jan 16 16:41:54 2001

Your knowlege of this is so far beyond mine I can barely follow. Even
that is too complimentary to describe the gap, but I'd rather not
discourage you by measuring the gap. In this I follow.

I was suggesting a software approach (virtual mmu), but the Atari XE has a
fairly capable mmu in that it allows multiple processors to access memory
separately without the intervention of the cpu. I think a combination of
custom software and this hardware would perform better than a solely
software approach would. I could well be wrong, but with my limited
knowlege it is hard for me to find a fault in the argument. LUnix is a new
word for me. Any more info? I could search for it, but you seem to know
your stuff and that is a rare thing I'm not likely to find in a blind



In <200101162115.NAA11712_at_stockholm.ptloma.edu>, on 01/16/01
   at 05:41 PM, Cameron Kaiser <spectre_at_stockholm.ptloma.edu> said:

>> 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 C64.

>> 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!

Jeffrey S. Worley
Complete Computer Services, Inc.
30 Greenwood Rd.
Asheville, NC 28803
Visit our website at HTTP://www.Real-Techs.com
Received on Tue Jan 16 2001 - 16:41:54 GMT

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