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Old 06 September 2019, 20:35   #1
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Join Date: Dec 2004
Location: FRANCE
Age: 48
Posts: 3,317
Pacman - the Amiga conversion from the arcade game

Asman asked me to post info on that, since it was discussed on other threads.

So my project was to create a 1:1 port of Pacman which plays the same and all, at 50pfs, on amiga, reusing the work of the zx spectrum program which uses the arcade version.

As someone (mcgeezer) suggested, it should be possible to port the Z80 code to 68000 with a converter.

I found one, and compiled it and all (it was ooold), but there were a LOT of issues with the convert (I think it works well for SMALL programs that don't use low level asm things, like compressors, etc...)

It also has other limitations, the worst one is: it can only run from 0 to $8000 (it uses address registers in signed 16 bit mode)

The FRONTZ80 code and the converted program should reside in the lower 32K or
upper 32K of the MC68000's memory map for proper execution.
So if you convert a big enough program, you hit the limit. And pacman is around $4000 bytes long. With expansion of instructions + adding condition code checking which is different, you easily hit the limit.

So I'm giving that solution up after a few days. So now you know: it's not easy (I can share more details, the convert is far from perfect and a lot of other things are missing (I could have used a small converted example too..., even if MOTOROLA wrote it!)

BUT, what would be almost as efficient would be to run a Z80 emulator designed for 68000 and do the rest exactly the same way. Can someone point me to some Z80 emulator with asm source code?
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