Zilog Z80

The Zilog Z80 is an 8-bit microprocessor designed and manufactured by Zilog from 1976 onwards. It was widely used both in desktop and embedded computer designs as well as for defense purposes, and is one of the most popular CPUs of all time.
Zilog Z80 microprocessor.
Although Zilog made several attempts to move off the Z80 onto more powerful 16-bit (Zilog Z800, Zilog Z8000, Zilog Z180, Zilog Z280) and 32-bit (Zilog Z80000, Zilog Z380) platforms, other companies were offering CPUs in this performance range years earlier, and the Zilog chips never caught on. Zilog’s most recent CPU is the Zilog eZ80, a faster Z80 with a 16 MB addressing range.

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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.

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In East Germany, an unlicensed clone of the Z80, known as the U880, was manufactured. It was very popular and was used in Robotron's and VEB Mikroelektronik MГјhlhausen's computer systems (e.g. the KC85-series) and also in many self-made computer systems (ex. COMP JU+TER).

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T34BM1, a Soviet Z80 clone.
Also, several fully compatible analogues of Z80 were created in the Soviet Union, a notable one being the T34. Another Soviet clone, the KP580BM80, was an analogue of the Z80's predecessor, the Intel 8080.

Today, a functionally equivalent CPU core (T80 & TV80) is available for free under a BSD style license as VHDL and Verilog 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.

By the early 1980s it was used in a host of home computer designs including the MSX, Radio-Shack TRS-80, Sinclair ZX80 & ZX81[3] and ZX Spectrum. It was also featured in the Osborne 1, the Kaypro, and a great number of fairly anonymous business-oriented CP/M machines 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. The Z80 was also used in the Norwegian Tiki 100 computers, which were the computers of choice for Norwegian schools during the late 1980s.

In Romania, several Z80 implementations 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 models were the most popular models.

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.

The Multitech Microprofessor I, introduced in 1981, is a simple and inexpensive training system for the Z80 microprocessor. As of early 2005, it is still on market.

Notable later uses of the processor include several Texas Instruments (TI) graphing calculators (like the TI-83 series, TI-84 series, and TI-85), 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. Many classic coin-op arcade games used the Z80 as a main CPU or sound coprocessor. An extreme example of the Z80's miniaturization is demonstrated by the Sega Dreamcast: Its Visual Memory Unit memory card was also a miniature video game with a Z80 processor!

 

ATX

ATX form motherboards became increasingly popular because of their advantages over older AT motherboards.
The ATX form factor was created by Intel in 1995. It was the first big change in computer case and motherboard design in many years. ATX overtook AT completely as the default form factor for new systems. Some related designs include mini-ITX and microATX. ATX addressed many of the AT form factor's annoyances that had frustrated system builders. In 2003, Intel announced the new BTX standard, intended as a replacement for ATX, but as of late 2005 the ATX form factor remains the industry standard.

AT-style computer cases had a power button that was directly connected to the system power supply unit (PSU). The general configuration had four pins that had to be connected individually. Sometimes, the pins were soldered to the power button, making it difficult to replace the power supply if it failed, or if the fan inside the PSU seized up. An ATX power supply doesn't directly connect to the system power button, allowing the computer to be powered off via software. However, many ATX power supplies have a switch on the back to ensure no power is flowing to the motherboard (a trickle of energy is normally sent to an ATX-style motherboard even if the computer appears to be "off"). Since the ATX PSU uses the motherboard's power switch, to turn on the power for use in situations that do not utilize an ATX motherboard it is possible to activate the power supply by shorting the green wire from the ATX connector to any black wire on the connector (or ground).