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Computer History: From The Antikythera Mechanism To The Modern Era

Commodore PET And TRS-80

Commodore International enjoyed popularity during the 1980s and 90s thanks to its Amiga home computer line. In 1977 Commodore released the PET (Personal Electronic Transactor) computer series. The first model of the PET line, the PET 2001, was the first home computer and was based on the MOS 6502 CPU, which controlled all of the peripheral devices connected to the system.

The PET 2001 was an 8-bit, single-board computer and like many computers of this era, it used a cassette tape recorder for data input/output. The first PET was announced at CES (Consumer Electronics Show) in January 1977, and its production started that same year. The PET 2001 was a success and in 1979 a new version, the 2001-N, was introduced. The PET 2001-N introduced a new innovation: the support for a disk drive line, which was made by Commodore. The disk drive was connected to the PET through an IEEE 488 interface.

In 1980 the 8-bit Commodore VIC-20 was released, and it used the MOS 6502 CPU and managed to sell a million units! The VIC-20 had 20KB of ROM and 5KB of RAM. Only 3.5KB of RAM was available to the user, because the remaining 1.5KB was used by the system for various tasks. In addition, there was a ROM cartridge port that allowed the plug-in of cartridges loaded with games or applications. Through this port the computer's limited memory could be upgraded to up to 32KB, and there were also port expanded boxes that allowed the attachment of more than one cartridge at the same time. VIC's production ceased at the beginning of 1985. The VIC-20's successor was the Commodore 64, which was introduced in 1982.


In 1977, the same year as the Commodore PET was released, Tandy/Radio Shack's TRS-80 made its debut. It used a Zilog Z80 CPU that was supported by 4KB of RAM and 4KB of ROM, along with a keyboard and a cassette tape recorder. Back in those days the TRS-80, along with the Commodore PET 2001 and the Apple II, were considered to be the most popular microcomputers. The TRS-80 was made by a member of the Homebrew Computer Club, named Steve Leininger. This club was a hobbyist group in Silicon Valley that included many notable computer entrepreneurs like the founders of Apple, John Draper, Roger Melen, Adam Osborne and many more.

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The TRS-80 was very successful and continued to sell until 1982. It easily took the lead from the more expensive Apple II, at least during the first five years. A key part of this was surely Radio Shack's large distribution network. Finally, one of the first microcomputer word processors was developed for the TRS-80 and it was called the Electric Pencil.

Aris Mpitziopoulos
Contributing Editor

Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.