The 486 is very similar to its predecessor, the 386. Main differences are an optimised instruction set, an on-chip unified instruction and data cache, an optional on-chip floating-point unit (FPU), and an enhanced bus interface unit. These improvements yield a rough doubling in performance over an 386 at the same clock rate.
There are several suffixes and variants including:
The 486 processor has been licensed or reverse engineered by other companies such as IBM, AMD and Cyrix.
Some manufacturers made hybrid 386/486 CPUs (Cxrix Cx486DLC, Texas Instruments TX486DLC), having a 486 instruction set and a 386-compatible pinout.
- 486SX - 486 with its FPU disabled
- 486DX - 486 with a working FPU
- 486DX-2 - runs at twice the external clock rate
- 486SL - 486DX with power conservation circuitry
- 486SL-NM - 486SX with power conservation circuitry
- 487 - 486DX with slightly different pinout for use in 486SX systems as FPU
- OverDrive - 486DX-2 with slightly different pinout for use in 486SX systems
- RapidCAD - 486DX in a special package with a companion FPU dummy package for use in 386 systems
- 486DLC - mix version by some manufacturers, featuring a 486 instruction set and a 386-compatible pinout
For more Information on x86 processors please refer to the x86 processor FAQ or CPU+Mainboard FAQ (german).