Happy 42nd Anniversary to the Original Intel 8086 and the x86 Architecture
Forty-two years ago today, Intel launched the original 8086 microprocessor — the grandfather of every x86 CPU ever built, including the ones we use now. This, it must be noted, is more or less the opposite outcome of what everyone expected at the time, including Intel.
According to Stephen P. Morse, who led the 8086 development effort, the new CPU “was intended to be short-lived and not have any successors.” Intel’s original goal with the 8086 was to improve overall performance relative to previous products while retaining source compatibility with earlier products (meaning assembly language for the 8008, 8080, or 8085 could be run on the 8086 after being recompiled). It offered faster overall performance than the 8080 or 8085 and could address up to 1MB of RAM (the 8085 topped out at 64KB). It contained eight 16-bit registers, which is where the x86 abbreviation comes from in the first place, and was originally offered at a clock speed of 5MHz (later versions were clocked as high as 10MHz).
Morse had experience in software as well as hardware and, as this historical retrospective makes clear, made decisions intended to make it easy to maintain backwards compatibility with earlier Intel products. He even notes that had he known he was inventing an architecture that would power computing for the next 40 years, he would’ve done some things differently, including using a symmetric register structure and avoiding segmented addressing. Initially, the 8086 was intended to be a stopgap product while Intel worked feverishly to finish its real next-generation microprocessor — the iAPX 432, Intel’s first 32-bit microprocessor. When sales of the 8086 began to slip in 1979, Intel made the decision to launch a massive marketing operation around the chip, dubbed Operation Crush. The goal? Drive adoption of the 8086 over and above competing products made by Motorola and Zilog (the latter founded by former Intel employees, including Federico Faggin, lead architect on the first microprocessor, Intel’s 4004). Project Crush was quite successful and is credited with spurring IBM to adopt the 8088 (a cut-down 8086 with an 8-bit bus) for the first IBM PC.
