A 34-year-old Apple Mac crash bug ‘would have gone undiscovered for all eternity,’ but the accuracy of the MAME emulator shone a light on it

A 34-year-old Apple Mac bug was discovered by a computing enthusiast, Downtown Doug Brown, thanks to the MAME emulator revealing a crash that the original hardware did not experience. The bug in the Mac Classic II ROM code was neutralized by an undocumented feature in the Motorola CPU, which prevented the system from crashing at startup. Brown's investigation revealed that the bug was present in the ROM code itself, not the emulation software. MAME has since patched the bug, and Brown speculates that there may not be a perfect emulator or replica of the Motorola MC68030 due to this undocumented feature.