Zilog Z80

The Z80 quickly took over from the 8080 in the market, and became the most popular 8-bit CPU of all time - indeed, if one takes the absolute size of the market into account, the most successful CPU ever. Later versions increased in speed from the early models' 2.5 MHz up to as much as 20 MHz.

Perhaps key to the success of the Z80 was the built-in DRAM controller, which allowed systems to be built with fewer support chips. Competitor MOS Technology, Inc, maker of the famous 6502 processor, later included this very useful feature in its second generation color video chip VIC-II.

Second sources and clones

Mostek and SGS were second-sources for the Z80. Sharp and NEC developed Z80 clones. National Semiconductor developed a CMOS clone, the NSC800, which was not pin compatible. Hitachi developed an enhanced CMOS version which later was second-sourced by Zilog.

Notable uses

By the early 1980s it was used in a host of home computer designs including the MSX, Radio-Shack TRS-80, Sinclair ZX80* & ZX81* and ZX Spectrum. It also featured in the great number of fairly anonymous business-oriented CP/M machines (plus the non-anonymous Osborne 1) that dominated the market of the time in the way that Windows-based machines do today. In the mid-1980s the Z80 was used in Tatung's Einstein and the Amstrad CPC and PCW home/office computer ranges as well as forming the CPU basis for the MSX computer standard.

Such was the popularity of the Z80 and CP/M that the Commodore 128 featured a Z80 processor alongside its MOS Technology 8502 processor for compatibility. Other 6502 based computers already on the market such as the BBC Micro, Apple II and the 6510 based Commodore 64 can make use of the Z80 with an external unit or a plug-in card or cartridge.

Notable later uses of the processor include several Texas Instruments (TI) graphing calculators (like the TI-85 and TI-83), and SEGA's Master System and Game Gear video game consoles. Both the SNK Neo-Geo and Sega Mega Drive/Genesis consoles use it as an audio coprocessor. Nintendo's Game Boy and Game Boy Color handheld game systems used a Z80 clone manufactured by Sharp Corporation, which had a slightly different instruction set. The Sharp Z80 in the Game Boy Color is notable for its ability to selectively double its clock speed when running Game Boy Color software. The Zilog Z80 has also become a popular embedded microprocessor and microcontroller core, where it remains in widespread use today.

In East Germany, an unlicenced clone of the Z80, known as the U880, was manufactured. It was very popular and was used in Robotron's and VEB Mikroelektronik Mühlhausen's computer systems (e.g. the KC85-series) and also in many self-made computer systems (ex. COMP JU+TER). In Romania, several Z80 clones were manufactured: HC85, HC90, HC91, HC2000 (by the Felix Computers Factory, based in Bucharest) and TimS (by the Timisoara Technical University). The HC85 and TimS clones were the most popular models.

A functionally equivalent CPU core (T80 & TV80) is available for free under a BSD style license as VHDL [1] and Verilog [1] source. The VHDL version, once synthesized, can be clocked up to 35 Mhz on a Xilinx Spartan II FPGA.
Software emulation of the Z80 instruction set on modern PCs runs faster than the original Z80 CPU ran and is used today with the MAME video game emulator's execution of 1980's vintage video games.

(* The Sinclair ZX80 and -81 were equipped with the Z80 clone NEC uPD780C.)

See also: List of home computers by category

External links