Sega Master System / Mark III / Game Gear
The known differences between the v0 and v1 ROMs are:
0x9f, 0xbf, 0xdf, 0xffto port
0x7f), for some reason this does not always work. v1 has a workaround for this bug: it moves the muting code into the IRQ handler, writing the bytes on every interrupt (once per frame?) while the game is paused.
rl c; rl c; rr c; rr c, starting at address
It is unknown whether there are any other differences between the ROMs.
Researched by Paul Baker