FastROM

FastROM is 3.58 MHz. It is about 33% faster than SlowROM. FastROM is a property of the ROM chip itself and not the board it is soldered onto.^[2] When the 5A22 is operating at fastROM speed, there are 6 master clock cycles per CPU machine cycles.

FastROM speeds only apply to the upper halves of banks $80-bf and all of banks $c0-ff.^[1]

The SAS cannot use FastROM.^[3] Games which utilize fastrom should indicate this at bit 4 of FFD5 of the cartridge header.^[4]