Re: converting assembler from one cpu to another ?


<robertwessel2@xxxxxxxxx> wrote in message
news:1171492894.875720.35490@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Feb 14, 3:51 pm, "Rod Pemberton" <do_not_h...@xxxxxxxxxxx> wrote:
Unlike the 6502, the x86 isn't "orthogonal," i.e.,
certain addressing modes only exist for certain instructions. This
could be
one (trivial) problem translating 6502 to x86.


Calling the 6502 orthogonal is *really* a stretch.

:-)

I've got very new memories of x86, and very old of 6502... which are
probably somewhat romanticized... ;-)

It was more
regular than the 8080, but that's not saying very much. 32 bit x86 is
much more orthogonal than the 6502 is (not that I'd call any version
of x86 particularly orthogonal), and even the 16 bit stuff is
debatable.


But, seriously, the way I remember the 6502 (6510 actually) was that all
those addressing modes applied to nearly every instruction, i.e., mostly
orthogonal. Or, perhaps that was only acumulator instructions, well, memory
fades... Today, I really couldn't tell you what the registers were called
or how many registers there were without looking it up. I remember
zero-page addressing, jsr/rts, and the basic operation of various
instructions and that's about all. If I saw a good reference, it'd probably
all come flashing back. Anyway, that was part of the reason I mentioned the
Transactor and C=Hacking articles, so he'd have some accurate documentation
from the era instead of my faded/jaded memories...


Rod Pemberton


.

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