Intel 80387SX

Introduced in 1987,[1] it was used to perform floating-point arithmetic operations directly in hardware.

The 387SX uses a 68-pin PLCC socket, just like some variants of the 80286 and the less common 80186 CPU, and was made in speeds ranging from 16 MHz to 33 MHz, matching the clock speed range of the Intel manufactured 386SX.

Some chips like the IIT 3C87SX could get up to 40 MHz, matching the clock speeds of the fastest 386SX CPUs.

[2] Intel released the low power version of 387SX coprocessor.

[4] The 25-MHz Intel387 SX math coprocessor was available in manufacturer's suggested retail price of USD $189.