2 Sep
2006
2 Sep
'06
6:19 p.m.
Ray Arachelian wrote:
Doug Coward wrote:
Oops, I just realized that I made this very unclear!
"They sure did" refers to unimplemented opcode use, which worked just
fine on the C128. This wasn't meant to say that the C128 had problems
with unimplemented opcodes.
Or rather, we should say undocumented opcodes as they were clearly
implemented. If you look closely at the 6502 opcode chart patterns
there are some missing ones, these are actually there, but they were
buggy in early 6500 series CPU's, so they were purposefully not documented.
Certain folks saw the patterns and recognized that there should have
been opcodes there and tried them, they worked. So they used them to
prevent reverse engineering. :-)
Remember that many pieces of C64 software back
then used unimplemented
opcodes in their protection schemes. I don't believe that the C128 had
any problem with this software.
They sure did. I saw lots of strange and wonderful things. The GEOS