The Zilog Z80 is an 8-bit microprocessor introduced in July 1976. It was widely used both in desktop and embedded computer designs as well as for defense purposes,
and is one of the most popular CPUs of all time.
It was designed (by Federico Faggin and Masatoshi Shima) to be binary compatible with the Intel 8080 so that most 8080 code
could run unmodified on it, notably the CP/M operating system.
The Z80 offered eight real improvements over the 8080:
The Z80 quickly took over from the 8080 in the market, and became one of the most popular 8-bit CPUs.
Later versions increased in speed from the early models' 2.5 MHz up to as much as 25 MHz.
- An enhanced instruction set (80 new instructions)
- Two separate register files, which could be quickly switched, to speed up response to interrupts
- Block move, block I/O, and byte search instructions
- Bit manipulation instructions
- A built-in DRAM refresh address counter that would otherwise have to be provided by external circuitry
- Single 5 Volt power supply
- Fewer outboard support chips required for clock generation and interface to memory and I/O
- A much lower price
It was second sourced and cloned by many companies like Mostek (as MK3880), NEC (as D780C),
SGS, Sharp (as LH0080) and Toshiba (as TMPZ84).
Clones of this processor were manufactured in East Germany (as U880), Romania and the Soviet Union.
In the early 1980s the Z80 was very popular in 8-bit computer designs, e.g.
and literally hundreds of others.