[Tuxnes-devel] CPU core graft

[Jim U. <ji...@3e...>]

Hello,

I'm looking at porting tuxnes to the Sega Dreamcast.
The first stumbling block is of course the heavy
dependence on the x86 instruction set, due to the
dynamic recompiler.

For this reason, I have grafted a portable cpu core
(currently Marat's M6502) into tuxnes.  Since I just
got it running yesterday, I haven't completely
genericized the interface to allow plugging in any cpu
core.  However, any core with the equivalent of read,
write, and loop (irq check) operations should now be
really easy to port.

The changes to get Marat's core to work were: implement
Read6502, Write6502, and Loop6502 operations; create C
functions to perform certain calculations previously
done (in assembly language) in INPUT:, OUTPUT:, NMI:,
and the MMC asm linkage functions; and a one-line
change to M6502.c for convenience.  There might be
other minor stuff.

I'm pretty sure Marat's license is incompatible with
the GPL, but the glue between tuxnes and the new cpu
core, being written by me, is. ;)

I've seen slight graphical glitches (the last line of
the status bar in Zelda sometimes gets corrupted, and
the map in Wizards and Warriors is slightly corrupted).
These may be my fault, or the tuxnes code may have been
dependent on peculiarities in the old asm code [tuxnes
has really WEIRD timing code, so I wouldn't rule this
out].

Let me know if anybody is interested in looking at the
code, even in its kind of haphazard state.

Jim

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