The Apple I had a single 256 byte bipolar PROM for its WozMon debugger. Though the Apple II used ROMs (EPROMS were popular in clones) the expansion cards still

The Apple I had a single 256 byte bipolar PROM for its WozMon debugger. Though the Apple II used ROMs (EPROMS were popular in clones) the expansion cards still were supposed to use tiny PROMs for their drivers (in the case of the disk controller there was even a second PROM for the state machine - Woz did love these devices). The Altair 680 had sockets for four 256 byte PROMs. One was for the debugger, but a popular option for the other three was the VTL-2 (very tiny language) interpreter. Pretty amazing that they fit a Basic-like language in just 768 bytes, though implementing some language in the 510 byte boot sector has become a popular hobby.