Description:

The MMI 341-0027-00 is a vintage 256 x 8-bit bipolar PROM (Programmable Read-Only Memory) used as the P5 “BOOT” ROM on the Apple Disk II 16-sector interface card. Developed around 1979 and marked with Apple’s copyright, this chip played a critical role in initializing the disk controller and loading the bootloader into memory on early Apple II systems. It’s a one-time programmable device, meaning its contents were factory-programmed or burned once and could not be altered—ideal for stable, unchanging firmware.