Numeric Coprocessor; Real-Address Operating Mode - HP Vectra Reference Manual

SECTION 8. NUMERIC
COPROCESSOR
HP45977A is the Intel 80287 numeric coprocessor chip that
enables HP Vedra PC to perform high-speed mathematical
functions with seven numeric data types. This section will provide
an overview to the 80287. For detailed information on this chip
refer to the bibliography for source material.
The coprocessor works in parallel with the 80286 microprocessor.
The parallel operation increases execution speed by allowing the
coprocessor to do mathematical calculations while the
microprocessor continues to do other routines. Similar to the
80286, the 80287 has two operating modes.
Real-Address Operating Mode
The system is in real-address mode at power-up. An I/O write to
port OF1 H with D7 through DO equal to 0 will reset the 80287,
and also place it in real-address mode. Real-address mode of the
80287 is compatible with the 8087 numeric coprocessor used in
many industry standard personal computers.
Numeric Coprocessor 99