Concept

Intel 8087

Summary
The Intel 8087, announced in 1980, was the first floating-point coprocessor for the 8086 line of microprocessors. The purpose of the chip was to speed up floating-point arithmetic operations, such as addition, subtraction, multiplication, division, and square root. It also computes transcendental functions such as exponential, logarithmic or trigonometric calculations. The performance enhancements were from approximately 20% to over 500%, depending on the specific application. The 8087 could perform about 50,000 FLOPS using around 2.4 watts. The 8087 was an advanced integrated circuit, pushing the limits of manufacturing technology of the period. Basic operations on the 8087 such as addition and subtraction can take over 100 machine cycles to execute and some instructions exceed 1000 cycles. The chip lacks a hardware multiplier and implements calculations using the CORDIC algorithm. Sales of the 8087 received a significant boost when a coprocessor socket was included on the 1981 IBM PC motherboard. Development of the 8087 led to the IEEE 754-1985 standard for floating-point arithmetic. There were later x87 coprocessors for the 80186, 80286, 80386, and 80386SX processors. Starting with the 80486, the later Intel x86 processors did not use a separate floating-point coprocessor; floating-point functions were integrated with the processor. 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 initially conceived by Bill Pohlman, the engineering manager at Intel who oversaw the development of the 8086 chip. Bill took steps to be sure that the 8086 chip could support a yet-to-be-developed math chip. In 1977 Pohlman got the go ahead to design the 8087 math chip. Bruce Ravenel was assigned as architect, and John Palmer was hired to be co-architect and mathematician for the project.
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