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Processor Zilog 8001 on the motherboard of an Olivetti M20 computer
Z8001 clone MME UB8001C made in GDR.

The Z8000 is a 16-bit microprocessor introduced by Zilog in 1979. The architecture was designed by Bernard Peuto while the logic and physical implementation was done by Masatoshi Shima, assisted by a small group of people. Z8000 was not Z80-compatible, and although it saw steady use well into the 1990s, it was not very widely used. However, the Z16C01 and Z16C02 Serial Communication Controllers still use the Z8000 core.


Although fundamentally a 16-bit architecture, some versions had 7-bit, segment registers that extended the address space to 8 megabytes.

The register set consisted of sixteen 16-bit registers, and there were instructions that could use them as 8-bit, 16-bit, 32-bit, and 64-bit registers. The register set was completely orthogonal, with register 15 conventionally designated as stack pointer, and register 14 for stack segment.

There was both a user mode and a supervisor mode.

Like the Z80, the Z8000 included built-in DRAM refresh circuitry. Although an attractive feature for designers of the time, overall the Z8000 was not especially fast and had some bugs, and in the end it was overshadowed by the x86 family.

One notable use of the Z8000 series was by Namco in the design of its famous Pole Position series of racing videogames. Two Z8002's (small-memory versions of the Z8000) were incorporated into the design.

The reported inclusion of the device within military designs, perhaps provides an explanation for the continued survival of the Z8000 today, in the shape of the Z16C01/02 Serial Communication Controllers (Zilog SCC). Indeed, an active order code and datasheet may still be located upon the Zilog website.

The Zilog Z80000 was a 32-bit follow-on design.

Z8000 CPU based systems

In the early 1980s, the Zilog Z8000 CPU was popular for desktop sized Unix machines. They allowed small businesses to run a true multi-user system and share resources (disk, printers) before networking was common. They usually had only RS232 serial ports (4-16) and parallel printer ports instead of built in graphics, as was typical for servers of the time.

Z8000-based computer systems included Zilog's own System 8000 series, as well as other manufacturers:
  • Jan 1980: Z8000 ONYX, 1st Unix workstation, demoed (8 serial ports [users], $25k)
  • Other Z8000-based computer systems: Olivetti M20, M30, M40, M50, M60
  • The Z8000 can be found in some rare but well-known computers, such as the Olivetti M20 and M40, and the Unix-based Commodore 900. Some third parties also manufactured the Z8000 including AMDmarker, SGS-Ates, Hitachi and Sharp.

There was a Z8000 version of the Xenix Operating System

The Z8000 CPU series was introduced in early 1979, between the launch of the Intel 8086 (April 1978) and the Motorola 68000 (September 1979). That explains the timeframe and why the Z8000 CPU-based systems lost their dominance to Motorola 68000 based machines, then to the Intel 80286.


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