6.2 Using a Math Coprocessor

When used with real numbers, packed BCD numbers, or long integers, coprocessors (the 8087, 80287, 80387, and 80486) calculate many times faster than the 8086-based processors. The coprocessor handles data with its own registers. The organization of these registers reflects four possible formats for using operands (as explained in Section 6.2.2, “Instruction and Operand Formats”).

This section also describes how the coprocessor performs various tasks: transferring data to and from the coprocessor, coordinating processor and coprocessor operations, and controlling program flow.