"The 80287 (i287) is the math coprocessor for the Intel 80286 series of microprocessors. Intel's models included variants with specified upper frequency limits ranging from 6 up to 12 MHz. Later followed the i80287XL with 387 microarchitecture and the i80287XLT, a special version intended for laptops, as well as other variants. The 80287XL is actually an 80387SX with a 287 pinout. It contains an internal 3/2 multiplier so that motherboards which ran the coprocessor at 2/3 CPU speed could instead run the FPU at the same speed of the CPU. Other 287 models with 387-like performance are the Intel 80C287, built using CHMOS III, and the AMD 80EC287 manufactured in AMD's CMOS process, using only fully static gates.
The 80287 and 80287XL work with the 80386 microprocessor, and were initially the only coprocessors available for the 80386 until the introduction of the 80387 in 1987. Finally, they were able to work with the Cyrix Cx486SLC. However, for both of these chips the 80387 is strongly preferred for its higher performance and the greater capability of its instruction set."
in case anyone is interested. (obviously a 386 board would need to have the appropriate socket)
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