Zilog Z80

Zilog · 1976 · Zilog Z80 CPU

The Z80 powered the ZX Spectrum and Game Boy — two of gaming's most culturally significant platforms — as well as the Sega Master System and Game Gear. Federico Faggin's design was an enhanced Intel 8080 that became the 8-bit era's workhorse.

The Zilog Z80 was designed by Federico Faggin and Masatoshi Shima, who had previously designed the Intel 8080. The Z80 extended the 8080 instruction set, added two index registers (IX and IY), provided an alternative register set that could be swapped with the primary registers for fast interrupt handling, and included a built-in memory refresh controller that simplified system design. The processor was simultaneously simpler and more capable than its Intel counterpart, and its lower cost — Zilog licensed it aggressively to hardware manufacturers — made it the most widely used 8-bit processor in consumer electronics through the late 1970s and 1980s. Clive Sinclair's decision to use the Z80 in the ZX Spectrum (1982) made it the architecture for Britain's dominant home computing platform; the Z80's instruction set became the programming language of an entire generation of UK software developers. Nintendo's choice of a custom Sharp LR35902 — essentially a Z80 variant combined with some 8080 elements — for the Game Boy (1989) meant that the Z80 architecture powered the most successful handheld gaming platform in history through more than a decade of commercial operation. The Sega Master System and Game Gear used full Z80 processors, maintaining architectural consistency across Sega's 8-bit platforms. The Sega Genesis included a Z80 as a secondary processor for backward compatibility with Master System software and to offload audio processing from the main 68000 CPU.