80287(HW) XENIX System V 80287(HW)
Name
80287 - Math coprocessor.
Description
The 80287 is the INTEL math co-processor for the 80286. The
kernel tests for the presence of an 80287 at startup.
If your system has an 80287, you must turn off a switch on
the main system board in order to enable 80287 interrupts.
Check your hardware manual to determine the proper switch
and setting. If your system does not have an 80287, or the
switch is on, the kernel will run a set of emulator routines
which are much slower.
The C compiler available with the program development
package generates the appropriate 8087 (or 80287) opcodes.
C routines compiled with this compiler have run as much as
200 times as fast as the emulated code. In particular, the
standard math library routines run considerably faster if
you have an 80287.
The overflow, division by zero, and invalid operand
exceptions return a SIGFPE signal. This signal can be
caught. The rest of the 80287 floating point exceptions
(underflow, denormalized operand, and precision error) are
masked.
Notes
The emulator returns meaningless information on divide by
zero.
There is no obvious way to tell which 80287 exception
generated the SIGFPE.
Page 1 (printed 2/7/91)