True, but SX used to stand (officially? dunno) for Singleword Xchange, as it had a 16 bit bus. DX was Doubleword Xchange, hence 32bit bus. Then in the 486, the

True, but SX used to stand (officially? dunno) for Singleword Xchange, as it had a 16 bit bus. DX was Doubleword Xchange, hence 32bit bus. Then in the 486, the bus was always 32-bit (at least from Intel. I have a faint memory of Cyrix 486SLCs with a 16bit bus), and now the SX-DX indicated the presence of an integrated FPU instead. Bonus: the 80487 was not just an FPU. It was a full 486DX which just disabled the main CPU and did all the work, and of course had an FPU.