In 1980, Intel introduced the 8087, a chip that made floating-point operations much faster in the IBM PC and other systems. Although the 8087 supports advanced operations such as tangents, square roots, and logarithms, this article focuses on basic arithmetic operations: addition and subtraction. The 8087 provided a spectacular speed improvement over the 8086 processor, speeding up addition by a factor of almost 100, and complicated operations by even more. In this article, I examine the 8087’s microcode and circuitry to explain exactly how floating-point addition and subtraction are implemented, including numerous special cases for infinities and other special values.
↫ Ken Shirriff
Shirriff took an actual chisel to the 8087 coprocessor to gain access to the insides for highly detailed photographs, taken with a microscope. They look amazing.
