Intel 8087 - Design and Development

Design and Development

Intel had previously manufactured the 8231 Arithmetic processing unit, and the 8232 Floating Point Processor. These were designed for use with 8080 or similar processors and used an 8-bit data bus. They were interfaced to a host system either through programmed I/O or a DMA controller.

The 8087 was released in 1980 and it had 45,000 transistors. It was manufactured as a 3 μm depletion load HMOS circuit. Intel production of the 8087 was done in Malaysia.

This coprocessor introduced about 60 new instructions, their assembly mnemonics all beginning with "F", to differentiate them from the 8086 integer instructions. For example, as a complement to ADD/MUL/CMP, the 8087 provided FADD/FMUL/FCOM. The binary encodings for all new instructions began with the bit pattern 11011, decimal 27, the same as the ASCII character ESC; similar instruction prefixes are also sometimes referred to as "escape codes".

Use of the coprocessor was not transparent to application programs, which had to be written to make use of the special floating point instructions. At run time, software could detect the coprocessor and use it for floating point operations; otherwise the function of the coprocessor was emulated in software.