2022-03-05 - An Incomplete History of Microprocessors

At the dawn of the computer age not only were they massive but their components were massive as well. Large collections of vacuum tubes or discrete transistors all wired together. A processor could fill a cabinet all by itself. The invention of integrated circuits allowed for all these components to be placed inside a single chip that could fit in your hand. Microprocessors are integrated circuits designed to process information and execute instructions. The shrinking of the processor lead in turn to the shrinking of the computer which allowed them to be used in homes and schools. Instead of needing a dedicated room computers could now fit on a desk. This list focuses on microprocessors used in consumer devices from the 70s and 80s.

1971 - Intel 4004

4-bit registers and data bus, 12-bit address bus (2048 bytes)

The 4004 was the first commercially produced microprocessor. Originally designed for calculators it soon became clear that it could be used to build a complete, if limited, computer

1974 – Intel 8080

8-bit registers and data bus, 16-bit address bus (64 kiB)

The 8008 was intel’s first 8-bit processor but it was the 8080 that really kicked off the microcomputer revolution. Computers like the Altair 8800 and the IMSAI 8080 were huge successes and lead to the standardization of the S-100 bus and CP/M as the first commercially available operating system.

1974 - Motorola 6800

8-bit registers and data bus, 16-bit address bus (64 kiB)

The 6800 found some use in early home computers like the Southwest Technical Products 6800 and the Altair 680 but it never caught on the way the 8080 did.

1975 - MOS Technology 6502

8-bit registers and data bus, 16-bit address bus (64 kiB)

Designed by former Motorola employees based on the 6800, the 6502 would go on to become one of the big players in the 8-bit micro generation. Used in computers like the Apple, the Apple II, the Commodore PET, the Atari 8-Bit family, and the BBC micro.

1976 - Texas Instruments TMS9900

16-bit registers, data bus and address bus (64 kiB)

Designed for use in TI own computer line-up the TMS9900 was one of the first 16-bit processors.

1976 - Zilog Z80

8-bit registers and data bus, 16-bit address bus (64 kiB)

Designed by former Intel employees and based in the 8080 the Z80 would become the other big microprocessor of the 8-bit era. It was used in computers like the TRS-80, Sinclair ZX80/ZX81/Spectrum and other business oriented computers. Being compatible with the 8080 it also ran CP/M.

1978 - Motorola 6809

16-bit registers, 8-bit data bus, 16-bit address bus (64 kiB)

The 6809 was similar to the 6800 but added some 16-bit features which gave it a step up over the other 8-bit processors of the time. It’s main use was in the TRS-80 Color Computer.

1979 – Intel 8088

16-bit registers, 8-bit data bus, 20-bit address bus (1 MiB)

The 8088 was used in the first-generation of IBM Personal Computers and is the grand-uncle of the modern x86 architectures which currently dominate the home computer market. It’s brother the 8086 had a full 16-bit data bus and was therefore faster but the 8088, with its smaller data bus, allowed for cheaper motherboards.

1979 - Motorola 68000

32-bit registers, 16-bit data bus, 24-bit address bus (16 MiB)

Although one of the first 32-bit processors the 68000 would become one of the main players in the 16-bit era of microcomputers with computers like the Apple Macintosh, Atari ST and Commodore Amiga.

1982 – MOS Technology 6510

8-bit registers and data bus, 16-bit address bus (64 kiB)

A modified version of the 6502 with I/O pins. The 6510 was used primarily in the extremely successful Commodore 64

1984 – Motorola 68020

32-bit registers, data bus and address bus (4 GiB)

A fully 32-bit version of the 68000 which found usage in revisions to the Apple Macintosh and Commodore Amiga lines.

1985 – Intel 80386

32-bit registers, data bus and address bus (4 GiB)

The first 32-bit implementation of the Intel x86 architecture that would become the mainstay of the PC world.