|Several Atari games used the ER-2055, or NI-7055, EAROM - electrically alterable read only memory, this was an 'also ran' technology which, according to history, lost out to EEPROM and later Flash memories. Anyway history aside one problem with these chips is they need an uncommon write voltage, -29v !!
So if you have a JAMMA adapter for Dig Dug, Millipede,Centipede or even if you've just replaced the original power supply in one of these games and don't have all the voltages available, the high-score saving feature won't work (!)
The solution is this plug in EAROM replacement board, it remaps the pinout of the EAROM to use a standard EEPROM without the need for any special voltages.
It plugs into the EAROM socket of the games with no additional wiring of hacking of the board.