Re: 6502 Recompiled

On Fri, Oct 15, 2004 at 12:17:38PM -0500, Graham Toal wrote:
> This is a _low-level_ translation of the assembly code into C, on an
> instruction by instruction basis. For example "Lda #42" would be
> replaced with "A=42;". It does indeed make it easier to port a
> game to another platform, but you do still need a good understanding
> of the original assembly code in order to do so.

This decompiling/recompiling may not be as easy as it sounds. I listened
to a talk by old Atari arcade programmers, and the did a lot of tricky
stuff to keep the boards from being bootlegged. One of them (I think
it was Owen Rubin.. programmer of Space Duel) said that he things like
noticing that " A" was the same as a JMP instruction in 6502, and so he
would jump into the memory containing the atari copyright message and
depend on it jumping back out again.. but I doubt a recompiled version
would do the right thing. Either it'd be jumping into the original
6502 code, or it'd be compiling the static strings and that means that
it wouldn't work properly.

Quite frankly, getting a 60Mhz embedded processor to emulate a 1Mhz 6502
shouldn't be that difficult. The virtualized hardware (like the AVG) will
be where you need to optimize.. not the main code.

  -- Mitch
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Received on Sat Oct 16 13:35:39 2004