3 Oct
2002
3 Oct
'02
10:33 a.m.
Ethan Dicks wrote:
--- Eric Smith <eric(a)brouhaha.com> wrote:
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. ;)
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.
-ethan
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