Remembering the Zilog Z80 Microprocessor
By James Grahame
It shouldn't surprise you that I have a fondness for a number of vintage microprocessors, including the 6502 used in the Apple II and the Motorola 68000 family used in the original Mac, Atari ST and Amiga systems. However, the CPU that means the most to me is the Z80.
Designed by Zilog and released in 1976, the 8-bit Z80 was one of the most popular processors of the late 1970s and early 1980s. Created by a couple of ex-Intel engineers, the Z80 used the familiar Intel 8080 instruction set and enhanced it with bit manipulation commands, block I/O, a single 5V power supply and on-board dynamic RAM refresh. The result was an affordable and familiar chip that was easier to design into products.
The Z80 was the heart of the Sinclair ZX80 and Radio Shack TRS-80 Model I computers -- the first micros my father purchased to fuel my lust for technology. The Z80 was also used in the ill-fated Coleco Adam, the Sinclair ZX Spectrum and Sinclair 2068, the Osbourne I portable and even the Commodore 128. Its popularity in the consumer field led to its invasion of military technology, too.
To add to the Z80's mystique, it didn't take young me long to discover that the Z80 also ran arcade machines such as Pac-Man, Galaga and Dig Dug (though the Galaga main board required three Z80s to handle its state-of-the-art graphics, sound and game play), along with home consoles such as the Sega Master System.
The Z80 is still alive and kicking in the 21st century, thanks to inexpensive derivatives (some available for under $1) that power countless consumer products.