8028x > IntelC80287XL_2
Modified: June 3, 2005, 7:13 pm
Data Code:9136
Package:40CDIP w/ Gold Lid
Process:1 Micron
Architecture:80 bit FPU
Used in:80286 Computers
Description:Intel 80287 is a co-processor for 80286 family of
processors. The 80287 has architecture similar to
Intel 8087, and it's completely object-code
compatible with the 8087 (but not pin-
compatible). The number of instructions and
execution time of instructions for both co-
processors is about the same. There are some
differences between the 80287 and 8087 FPUs:

The 80287 may run asynchronously from the main
processor. The 80286 processor divides external
clock by 2, while the co-processor divides it by
3. If both the 80286 and 80287 use the same
external clock it results in the co-processor
running at the 2/3 speed of the main processor.

When the main processor executes the FP
instructions it now checks if the co-processor is
busy, and, if necessary, will wait for the co-
processor to become available. As a result, it's
no longer necessary to add WAIT (FWAIT)
instruction before most of the 80287

The Intel 80287 was produced at speeds ranging
from 5 to 12 MHz. Other companies produced 16 MHz
and 20 MHz versions of the FPU.
AMD, Cyrix, and IIT also made 287's.

The 287XL is the new version of the 287. It is
made in CMOS and based on the 387. It is much
faster then the original.