CertiGuide to A+ (Core Hardware)  9  Chapter 0010:  CPUs       9  IV  Older CPUs (80386 and 80486 Class)

80386 1 Math Co-Processors

The 80386 CPUs were an amazing technical achievement, and luckily for Intel stockholders, priced as such. Everyone wanted a 386, even if they couldn't afford one. The marketing folks at Intel found a way to sell more 386's without hurting the profitability of the original 80386. Reduce the data path external to the CPU, making for a less expensive system board, add a suffix to the label 80386, oh, SX will do, and now more people can buy an 80386. This worked so well; Intel will use this idea again later.

Only one thing was missing in the 80386. That was the ability to do floating-point math.

80386 1 Math Co-Processors