The 8088

1979 · 16-Bit CPU, 8-Bit Bus · Work 909 of 1,871

An engineer's office in Haifa on a bright afternoon, at a desk of pale wood by an open window two hands in rolled-up white shirt sleeves holding side by side two identical long narrow chips of black-brown ceramic five centimetres long, each with twenty silvery legs along each side, a small notch at one end and a thin gold seam between the ceramic layers, both plain smooth and unmarked, on the desk a cup of black coffee, a pencil and a stack of ruled sheets lying face down, through the window a blue bay below a hillside of white houses and dark cypresses, warm Mediterranean light from the left.

What it was used for
The 8088 was an 8086 with half its data bus: 16 bits inside, 8 bits outside, so that it could work with the cheaper 8-bit parts around it. In his talk Stephen Morse describes it as identical to the 8086 in every respect except that half its data pins were cut off; the rework was done, according to IEEE Spectrum, by Intel's design group in Haifa. IBM chose it for the first PC. Spectrum gives 29,000 transistors and a price of 3,000 US dollars for IBM's Model 5150.
What was new
This processor was no technical step forward - that is the point. It did what the 8086 did, but needed fewer and cheaper support chips, according to IEEE Spectrum. The barb: the thriftier of the two variants settled the architecture question for decades, because IBM put it, not the full 8086, into the PC. Per Spectrum's piece on that chip, Motorola's 68000 was passed over partly because it was "still relatively scarce" - so the decision turned not on the best design but on availability and the cost of everything around it.

What the sources leave open: The figures come from the IEEE Spectrum Chip Hall of Fame piece (30 June 2017) and Morse's own account. A sentence quoted there from Robert Noyce and Ted Hoff was not used, because the original publication was not consulted. The 3,000 dollar price is for the IBM 5150, not the processor. The piece gives no clock speeds and no unit numbers.

Connections

Every connection names its kind. “Forerunner” on its own would be a claim.

  1. Follows fromThe 80861978Intel's 8086 Family User's Manual of October 1979 states that the execution unit of the 8086 and the 8088 is identical. The 8088 has an eight-bit external data path, while the 8086 transfers 16 bits at a time; in almost every other respect the two are identical. Software written for one of the two processors runs on the other without alteration.Source: Intel: The 8086 Family User's Manual, Bestellnummer 9800722-03, Oktober 1979, Abschnitt 2.1 (Bitsavers-Scan im Internet Archive)

Further reading