The successor to the 80386 processor, Intel 80486 (i486) added new important features:
Floating Point Unit was integrated with the processor
Internal clock doubling and tripling allowed the processor to run much faster in existing motherboards.
Power management features and SMM (System Management Mode) became a standard feature of the processor.
Instruction set optimization resulted in even greater performance of the processor. Different versions of the 80486 were produced, two most common versions are 80486DX with integrated FPU, and 80486SX without FPU. The Intel 80486 was produced at speeds up to 100 MHz. AMD produced even faster 120 and 133 MHz versions of the 80486.
Early SX chips had the FPU disabled, later ones had it removed from the die completely, saving 400,000 transistors.