Intel 8087 Math Coprocessor

In the IBM 5150/5155/5160, any 8087 fitted needs to be rated at 5 MHz, or better (higher).

Printed on chip Speed rating
8087 4MHZ 4 MHz
8087 5 MHz
8087-2 8 MHz
8087-1 10 MHz

Some people are under the impression that adding an 8087 to their motherboard (where applicable) will speed up their computer.
That impression is false.
The 8087 does not speed up hardware.  It will speed up software that is written to take advantage of the presence of an 8087.

The following threads at the Vintage Computer Forums discuss such software:

Thread #1     ("Software which can use 8087/80287 coprocessor?")
Thread #2     ("Programs that use the 8087")
Thread #3     ("Programs that use the 80287")