It&#x27;s implemented using a few standard 74xxx TTL logic chips and a 256x16 microcode ROM. It&#x27;s important not to ignore the microcode ROM because that&#x27;s where all the smarts that turn it from an ALU unit and a bunch of registers and miscellaneous logic into a CPU that can actually execute instructions. All of the instruction decoding and the sequencing of all the operations that make up a CPU cycle is done directly by the microcode ROM.