Can you port the theoretical code for adc/sbc TO the snes (without actually using decimal mode on the snes) and then have the snes sequentially do actual adc/sbc ops, then do software emulation, and compare the two (and throw an error to screen if they don't match)? I know MooglyGuy had something similar for testing mess's n64 rsp core vs the real one on the n64 itself, though I don't know what happened to it...
LN
