287XL ID

[a...@cruzio.santa-cruz.ca.us]

Intel 287XL is the successor to the old 287 supporting the ANSI/EEE
floating point standard. To a program the 287 XL appears to be a 387
with a 16 bit bus. This would not be a problem had Intel made it
impossible to add a 287 to a 386. Unfortunately regular cocpu ID routines
will mis-ID the 287XL as a 387; and if you have a 386-287XL combo
and try to use 32-bit ops, the result is far from satisfactory.

I have had some problems detecting a 287XL processor. What I've used
so far was to run the 287XL specific FRSTPM command and see if the
Invalid Op flag goes up. Unfortunately IIT's Math processors have
this command UNDEFINED. When you run FRSTPM the mathcpu locks up for
c. 200 cycles, and after that the only valid op is FNINIT; others get stuck.

So in essence I would like to know if anybody knows a clean way of
making sure that the cocpu is a 287 XL?

Aki.
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