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The 8087 was the first math coprocessor designed by Intel and it was built to be paired with the Intel 8088 and 8086 microprocessors. The purpose of the 8087, the first of the x87 family, was to speed up computations on demanding applications involving floating point mathematics. The performance enhancements went from 20% to 500% depending on the specific application.
This coprocessor introduced about 60 new instructions available to the programmer, all beginning with "F" to differentiate them from the standard 8086/88 integer math instructions. For example, in constrast to ADD/MUL, the 8087 provided FADD/FMUL.
The 8087 (and, in fact, the entire x87 family) does not provide a freely, linear register set such as the AX/BX/CX/DX registers of the 8086/88 and 80286 processors -- the x87 registers are structured in some form of stack (altough it is not exactly like a typical stack data structure) ranging from ST0 to ST7. The floating point instructions of the 80x87 coprocessors operate popping and pushing values onto this stack.
When Intel designed the 8087 aimed to make a standard floating point format for future designs. In fact, one of the most successful things from an historical perspective of this coprocessor was the introduction of the first floating point standard for the x86 PCs: the IEEE 754. The 8087 provided two basic 32/64-bit floating point data types and an additional extended 80-bit internal support to improve accuracy over large and complex calculations. Apart from this, the 8087 offered a 80-bit/17-digit packed BCD (binary coded decimal) format and 16,32 and 64-bit integer data types.
The 8087, announced in 1980, was superseded by the 80287, 80387DX/SX and the 487SX. Intel 80486, Pentium and later processor include a built-in coprocessor on the CPU core.
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