[ EARLY 8-BIT AND 16-BIT PROCESSORS // IDENTIFIED CPU ]
Zilog Z80A (4 MHz)
Zilog Z80 family introduced 1976; 4 MHz NMOS speed grade. 8-bit bus/ALU, 16-bit address, two register banks/index registers, 40-pin DIP, 4 MHz.
MODEL IDENTIFICATION: Zilog Z80A (4 MHz). Match full model suffix, stepping and package to the physical item and cited documentation.
Recorded specifications
| Cataloged model | Zilog Z80A (4 MHz) |
|---|---|
| Era / family | Zilog Z80 family introduced 1976; 4 MHz NMOS speed grade. |
| Model specifications | 8-bit bus/ALU, 16-bit address, two register banks/index registers, 40-pin DIP, 4 MHz. |
| Compatibility | Z80 bus/control timing required; shared 8080 subset is not pin compatibility. |
| Variants / limits | Z80B/CMOS Z84C00 have different ratings. |
Compatibility and variants
- Z80 bus/control timing required; shared 8080 subset is not pin compatibility.
- Z80B/CMOS Z84C00 have different ratings.
- Check system-vendor CPU support, board revision, firmware minimum, package, memory, cooling and power before installation; similar socket naming does not prove compatibility.
Service and archival notes
Record speed mark, oscillator, memory map and support chips.
Archive the complete marking/OPN/sSpec, stepping, physical condition, tested host revision, firmware, memory population, cooling, and test conditions. Distinguish published limits from measurements.
Sources & further reading
- Model lookup — Zilog Z80A (4 MHz)Model-specific package and specification cross-reference.
- Manufacturer technical documents — Zilog Z80A (4 MHz)Archived manufacturer data sheets/manuals for the exact family.
- Computer History Museum — Zilog Z80A (4 MHz) historyInstitutional history of early microprocessor development.
- Various Creators — Z80/Z180 Retro computer overview 2026Independent video review; treat as supplementary context, not primary manufacturer documentation.
Use the matching manufacturer data sheet revision and platform vendor’s CPU list for final fit decisions.