8087 emulation on 8086 systems

Not too long ago I had a need and an opportunity to re-acquaint myself with the mechanism used for software emulation of the 8087 FPU on 8086/8088 machines. ↫ Michal Necasek Look, when a Michal Necasek article starts out like this, you know you’re in for a learnin’ ol’ time. The 8087 was a floating-point coprocessor for the 8086 and 8088 processors, since back in those early days, processors did not include an integrated floating-point unit. It wouldn’t be until the release of the 486DX, in 1989, that Intel would integrate an FPU inside the processor itself, negating the need for a separate chip and socket. Interestingly enough, Intel also released a cut-down version of the 486 with the FPU removed, the 486SX, for which an optional external FPU did exist.