Software Emulation of the Intel 8087 FPU on 8086/8088 Systems: A Technical Retrospective
By
ingve
Pulled from the oven just right. Trustworthy, fact-dense, deeply satisfying.
Summary
The article explores the technical mechanism behind software emulation of the Intel 8087 FPU (Floating Point Unit) on 8086/8088 systems. It covers the 8086's generic co-processor interface, first used by the 8089 I/O processor and later the 8087 NPX (Numeric Processor Extension). The 8087 was an expensive add-on that required a dedicated socket, which not all systems had. The author discusses re-acquainting themselves with the software emulation approach used when the physical 8087 co-processor was unavailable.
Key quotes
· 3 pulledNot 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.
The 8086 CPU (1978) had a generic co-processor interface first utilized by the Intel 8089 I/O processor (1979) and later the Intel 8087 FPU (1980), initially called the Numeric Processor Extension or NPX.
The 8087 was a somewhat expensive add-on, assuming that a given system actually had a socket to plug the 8087 into (IBM PCs did, but other 8086/8088 systems did not necessarily have one).
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