The Z8000 is a 16-bit

16-bit

-16-bit architecture:The HP BPC, introduced in 1975, was the world's first 16-bit microprocessor. Prominent 16-bit processors include the PDP-11, Intel 8086, Intel 80286 and the WDC 65C816. The Intel 8088 was program-compatible with the Intel 8086, and was 16-bit in that its registers were 16...

 microprocessor

Microprocessor

A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...

 introduced by Zilog

Zilog

Zilog, Inc., previously known as ZiLOG , is a manufacturer of 8-bit and 24-bit microcontrollers, and is most famous for its Intel 8080-compatible Z80 series.-History:...

 in 1979. The architecture was designed by Bernard Peuto while the logic and physical implementation was done by Masatoshi Shima

Masatoshi Shima

is a Japanese electronics engineer, who was one of the designers of the world's first microprocessor, the Intel 4004, along with Federico Faggin, Ted Hoff, and Stanley Mazor....

, assisted by a small group of people. The Z8000 was not Z80

Zilog Z80

The Zilog Z80 is an 8-bit microprocessor designed by Zilog and sold from July 1976 onwards. It was widely used both in desktop and embedded computer designs as well as for military purposes...

-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.

Features

Although fundamentally a 16-bit architecture

Architecture

Architecture is both the process and product of planning, designing and construction. Architectural works, in the material form of buildings, are often perceived as cultural and political symbols and as works of art...

, some versions had 7-bit, segment registers that extended the address space to 8 megabytes.

The register set

Processor register

In computer architecture, a processor register is a small amount of storage available as part of a CPU or other digital processor. Such registers are addressed by mechanisms other than main memory and can be accessed more quickly...

 consisted of sixteen 16-bit registers, and there were instructions that could use them as 8-bit

8-bit

The first widely adopted 8-bit microprocessor was the Intel 8080, being used in many hobbyist computers of the late 1970s and early 1980s, often running the CP/M operating system. The Zilog Z80 and the Motorola 6800 were also used in similar computers...

, 16-bit, 32-bit

32-bit

The range of integer values that can be stored in 32 bits is 0 through 4,294,967,295. Hence, a processor with 32-bit memory addresses can directly access 4 GB of byte-addressable memory....

, and 64-bit

64-bit

64-bit is a word size that defines certain classes of computer architecture, buses, memory and CPUs, and by extension the software that runs on them. 64-bit CPUs have existed in supercomputers since the 1970s and in RISC-based workstations and servers since the early 1990s...

 registers. The register set was completely orthogonal, with register 15 conventionally designated as stack

Stack (data structure)

In computer science, a stack is a last in, first out abstract data type and linear data structure. A stack can have any abstract data type as an element, but is characterized by only three fundamental operations: push, pop and stack top. The push operation adds a new item to the top of the 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

Dram

Dram or DRAM may refer to:As a unit of measure:* Dram , an imperial unit of mass and volume* Armenian dram, a monetary unit* Dirham, a unit of currency in several Arab nationsOther uses:...

 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

Namco

is a Japanese corporation best known as a former video game developer and publisher. Following a merger with Bandai in September 2005, the two companies' game production assets were spun off into Namco Bandai Games on March 31, 2006. Namco Ltd. was re-established to continue domestic operation of...

 in the design of its famous Pole Position

Pole Position

Pole Position is a racing video game released in 1982 by Namco. It was published by Namco in Japan and by Atari, Inc. in the United States...

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

Military

A military is an organization authorized by its greater society to use lethal force, usually including use of weapons, in defending its country by combating actual or perceived threats. The military may have additional functions of use to its greater society, such as advancing a political agenda e.g...

 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

Zilog SCC

The Zilog Z16C01 SCC was introduced in the early 1980s and provided the ability to do both standard UART style serial communications along with the HDLC protocol for a reasonable price. It was a descendant of the earlier Zilog SIO, and its main enhancement was the inclusion of a built-in baud rate...

). Indeed, an active order code and datasheet may still be located upon the Zilog website.

The Zilog Z80000

Zilog Z80000

The Z80000 is Zilog's 32-bit processor from 1986, an expansion of its 16-bit predecessor, the Zilog Z8000. It includes multiprocessing capability, a six-stage instruction pipeline, and a 256-byte cache. Its memory addressing system can access 4 gigabytes of RAM. Described at the time as a...

 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: C8000 from Onyx Systems
  Onyx Systems
  Onyx Systems, Inc., founded in Cupertino, California in 1979 by Bob Marsh and Kip Myers, was one of the earliest vendors of microprocessor-based Unix systems...
  
  , early Unix multi-user system, demoed (8 serial ports [users], $25k)
• Other Z8000-based computer systems: Olivetti
  Olivetti
  Olivetti S.p.A. is an Italian manufacturer of computers, printers and other business machines.- Founding :The company was founded as a typewriter manufacturer in 1908 in Ivrea, near Turin, by Camillo Olivetti. The firm was mainly developed by his son Adriano Olivetti...
  
   M20, M30, M40, M50, M60
• The Z8000 can be found in some rare but well-known computers, such as the Unix-based Commodore 900
  Commodore 900
  The Commodore 900 was a prototype microcomputer intended for business computing and CAD purposes, and created by German Division of Commodore in 1985. The project was cancelled when Commodore bought Amiga. All of the prototypes were sold as scrap to 3rd party distributors...
  
  . Some third parties also manufactured the Z8000 including AMD, SGS-Ates
  STMicroelectronics
  STMicroelectronics is an Italian-French electronics and semiconductor manufacturer headquartered in Geneva, Switzerland.While STMicroelectronics corporate headquarters and the headquarters for EMEA region are based in Geneva, the holding company, STMicroelectronics N.V. is registered in Amsterdam,...
  
  , Toshiba
  Toshiba
  is a multinational electronics and electrical equipment corporation headquartered in Tokyo, Japan. It is a diversified manufacturer and marketer of electrical products, spanning information & communications equipment and systems, Internet-based solutions and services, electronic components and...
  
   and Sharp
  Sharp Corporation
  is a Japanese multinational corporation that designs and manufactures electronic products. Headquartered in Abeno-ku, Osaka, Japan, Sharp employs more than 55,580 people worldwide as of June 2011. The company was founded in September 1912 and takes its name from one of its founder's first...
  
  .

The Zilog S8000 computer came out with a version of Unix called ZEUS (Zilog Enhanced Unix System). This version of Unix was not based on Xenix but via Interactive. There may have been a Xenix version from some other company as back in 1979 Xenix was 8088/8086 based. ZEUS was a port of Unix Ver 7 and included what were referred to as 'the Berkeley Enhancements'. ZEUS included a version of cobol called RMCobol (Ryan McFarland Cobol). The availability of RMCobol allowed many commercial applications to be quickly ported to the S8000 computer although this did not help its long term success.

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.