Chip Hall of Fame: Intel 8088 Microprocessor

The “castrated” processor that birthed the IBM PC


Was there any one chip that propelled Intel into the Fortune 500? Intel says there was: the 8088. This was the 16-bit CPU that IBM chose for its original line of PCs, which went on to dominate the desktop computer market.

In an odd twist of fate, the chip that established what would become known as the x86 architecture didn’t have a name appended with an “86.” The 8088 was basically a slightly modified 8086, Intel’s first 16-bit CPU. Or as Intel engineer and 8086 designer Stephen Morse once put it, the 8088 was “a castrated version of the 8086.” That’s because the new chip’s main innovation wasn’t exactly a step forward in technical terms: The 8088 processed data internally in 16-bit chunks, but it used an 8-bit external data bus.

Intel managers kept the 8088 project under wraps until the 8086 design was mostly complete. “Management didn’t want to delay the 8086 by even a day by even telling us they had the 8088 variant in mind,” says Peter Stoll, a lead engineer for the 8086 project who did some work on the 8088.

Photo: Intel
With some favorable early press, Intel’s PR department was sure it had a winner.

It was only after the first functional 8086 came out that Intel shipped the 8086 artwork and documentation to a design unit in Haifa, Israel, where two engineers, Rafi Retter and Dany Star, altered the chip to an 8-bit bus.

The modification proved to be one of Intel’s best decisions. The 29 000-transistor 8088 CPU required fewer, less expensive support chips than the 8086 and had “full compatibility with 8-bit hardware, while also providing faster processing and a smooth transition to 16-bit processors,” as Intel’s Robert Noyce and Ted Hoff wrote in a 1981 article for IEEE Micro magazine.

The first PC to use the 8088 was IBM’s Model 5150, a monochrome machine that cost US $3,000. Now almost all the world’s PCs are built around CPUs that can claim the 8088 as an ancestor. Not bad for a castrated chip.