The Zilog Z80 has turned 50
Fifty years after its debut, the Zilog Z80 CPU is remembered as a foundational chip that introduced many people to low-level computing, from ZX Spectrum and TRS-80 micros to TI graphing calculators still used in schools today. Commenters reflect on learning assembly, hand-assembling opcodes, and reverse‑engineering ROMs, arguing that simple 8‑bit architectures like the Z80 remain invaluable for understanding computers “to the metal.” The thread also touches on its long production life, modern open-core clones, and contrasts with newer ISAs such as RISC‑V, especially around design choices like flag and overflow handling.
Personal histories and nostalgia
- Many commenters learned computing on Z80-based machines: ZX-81, ZX Spectrum, TRS-80, Timex, MSX, various Soviet clones, and home-built kits.
- Strong emotional attachment: people recall hand-assembling hex, typing programs from magazines, disassembling ROMs, and even keeping machines powered for weeks to avoid losing code.
- Several describe Z80 as their “first language” or “first love,” influencing entire careers in software, hardware, and entrepreneurship decades later.
Z80 as an educational platform
- Z80 assembly was often learned via BASIC first, mapping BASIC constructs to registers, jumps, and calls.
- Classic books and magazine columns on Z80 and general microcomputer architecture are cited as formative, helping people understand computers “down to the metal.”
- Some technical schools as late as 2003 still used Z80 to teach computer fundamentals.
TI calculators and standardization
- TI-83/84 graphing calculators (Z80/eZ80) are remembered as ubiquitous in US schools and some European countries, with students writing TI-BASIC and occasionally assembly.
- Debate: some see TI hardware as outrageously overpriced and obsolete; others argue that stability, curriculum alignment, and vendor lock-in with textbooks justify it.
- Other regions report Casio/HP dominance and less model standardization, sometimes with explicit bans on programmable calculators for exams.
Ongoing hardware, clones, and uses
- The original Z80 reportedly stopped production recently, but drop-in-compatible open cores and FOSS silicon projects exist, along with eZ80 successors.
- Z80 or Z80-like cores still appear in calculators, audio gear, sensors, and old MP3 players; Z80 is also emulated in browsers and hobby projects.
Architecture, compatibility, and ISA debates
- Discussion of 8080 compatibility notes flag differences and undefined opcodes; “binary compatible” is seen as true only within defined instructions and ignoring parity behavior.
- The Z80’s repurposing of parity as an overflow flag is praised as a useful extension.
- Long subthread contrasts Z80-style flags with RISC-V’s lack of condition flags. Some argue this makes safe arithmetic and multiprecision math inefficient; others counter that limb-based techniques, modern OoO designs, and benchmarks make the concern overblown.
Retro tools and ongoing projects
- People mention writing their own assemblers, using modern Z80 assemblers and emulators, and still planning or making new ZX Spectrum–style games and demos.