I'm trying to provide an instruction-accurate port of some code that runs on a 6502 CPU to x86. I'm pretty good on the x86 assembly side (though don't really know FPU opcodes or anything added since 1996), but know zip about the 6502 side of life.
At the moment I'm building a table that provides the x86 equivalent of 6502 instructions. Most are pretty straightforward (e.g. ADC = ADC), but others are a bit more of a mystery.
CLI clears the "interrupt disable" flag on a 6502, but the flag works the opposite (enable) on an Intel, so the equivalent is STI, yes?
I also have no clues about "decimal mode" on the 6502, whether that translates to anything at all on the Intel. Any ideas?
Quite handy that it only has three registers though (X, Y and SP), makes things fairly economical.