Re:Emulating the Original Gameboy’s CPU
by userbinator on Friday December 27, 2019 @05:05PM
(#21895153)
I suspect Nintendo may have started with a Z80 core and then customised it a little bit, similar to what they did with the almost-6502 in the NES.
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It's definitely based on the Z80, but it's also different enough that you can't really base yourself on Z80 docs to implement the Game Boy CPU (I learned that the hard way). The flags are different, the timings are different, some instructions are removed, some instructions are added etc...