Ethan Dicks wrote:
>
> --- Eric Smith <eric_at_brouhaha.com> wrote:
> > When Rockwell licensed the CMOS 6502 from WDC, they added their bit
> > manipuation instructions to it. Thus the Rockwell R65C02 has more
> > instructions than the "standard" 65C02 from WDC, GTE, NCR, and others.
>
> Speaking of the 65C02, does anyone know if replacing the 6502 in a PET
> or VIC-20 is known to trip up copy protection on any apps/games? I
> know that for well-behaved code, there should be no problems. I'm
> concerned about WordPro or some other pirate-fearing program trying
> to be clever with undocumented op codes, and not working with a real
> 65C02.
There's always the possibility, but CMOS versions would be
much
better candidates for such perverse cleverness than the old
NMOS parts. At least I vaguely recall that most if not all
unimplemented instructions for the NMOS 6502 either sent the
CPU
careening off into the weeds or were simple duplicates of
"legal"
op-codes due to incomplete op-decoding.
Hopefully others who know I'm full of beans can correct this
if it's wrong.
This is the impression I got from reading the MINI-DIS
listing
in The First Book of KIM (not with me at the moment),
anyways.
P.S.:
I think 512Kx8 for a KIM-1 is pretty cool, but I haven't
figured
out the best TLB/MMU and cache implementation. ;)
>
> -ethan
>
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Received on Thu Oct 03 2002 - 17:33:01 BST