The Zilog Z80 Turns 50: How an 8-Bit Workhorse Shaped Computing

Zilog’s Z80, launched in July 1976, is marking half a century since it became one of the most influential processors ever built. Binary-compatible with Intel’s 8080 and 8085, it anchored the 8-bit microcomputer era — powering early personal computers, home and hobby machines, and a long tail of industrial and embedded systems. That compatibility helped cement de facto standards up the stack: CP/M as an operating system and Microsoft BASIC as a language. The chip’s DNA spread through clones and derivatives, most famously the Sharp LR35902 at the heart of the original Game Boy, and Zilog eventually retreated from 16- and 32-bit ambitions back to Z80-based microcontrollers like the faster, pipelined eZ80. The original part stayed in production until Zilog finally discontinued it just two years ago.

The author frames the anniversary through personal history — designing a homebrew Z80 computer as a teenager, etching PCBs in a school photo lab, and collecting vintage chips (Z80s, 8085s, 6502s, MCS-85 parts) from teachers’ drawers. That tinkering doubled as a crash course in systems engineering, including hard-won lessons that reliable power-on reset is deceptively tricky and that writing a linker is harder than writing an assembler or even a compiler.

Much of the piece traces the lineage behind the chip. It starts with Computer Terminal Corporation’s Datapoint 2200, whose TTL-based 8-bit CPU inspired Intel’s single-chip 8008 — a design TI abandoned and CTC declined, leaving Intel to commercialize it. The 8008’s quirks (a 7-register set, an 8-level internal return stack chosen to avoid serial-memory bottlenecks, 14-bit addressing, RST-based interrupts, and awkward register-saving) drove the follow-on 8080, which Federico Faggin pushed for and staffed by hiring Masatoshi Shima from Busicom. The 8080 broke binary compatibility, moved the call stack into memory via a stack pointer, and widened addressing to a full 16 bits for a 64K space — the architectural groundwork the Z80 would later extend and dominate.