accurately emulate the functionality in some other freely available silicon
Get a cheap PIC or AVR microcontroller, put it on a DIP-sized carrier board, and write a program to simulate everything you’d see on the data/address and any other IO pins of the Z80 when they are manipulated. There you go, drop-in replacement.
Get a cheap PIC or AVR microcontroller, put it on a DIP-sized carrier board, and write a program to simulate everything you’d see on the data/address and any other IO pins of the Z80 when they are manipulated. There you go, drop-in replacement.