The 486DX was the original 486 and it definitely did include an FPU. The FPU-free 486SX came along a couple of years later. My recollection is that the SX was originally a way to make use of 486DX chips that failed manufacturing tests on the FPU; they'd disconnect the FPU portion of the die and sell the busted chips as "486SX". Same trick AMD pulled with the 3-core Phenom.
My apologies; I thought you were making a comment which was intended to be relevant to the one you were replying to, which concerned the change from the 386 to 486DX. I am not sure what relevance the configuration of the later 486SX would have to the situation msisk6 described.
