486SX

The i486SX was a microprocessor originally released by Intel in 1991. It was a modified Intel i486DX microprocessor with its floating-point unit (FPU) disabled. Priced at US$258, it was intended as a cheaper, lower-end option, denoted by the SX suffix, in line with the earlier i386SX. However, unlike the i386SX, which had a 16-bit external data bus and a 24-bit external address bus (compared to the fully 32-bit i386DX, its higher-end counterpart), the i486SX was entirely 32-bit. The Intel486 SX-20 CPU can perform up 20 MIPS at 25 MHz, 70% faster than the 33 MHz Intel386 DX with external cache. OverviewIn the early 1990s, common applications, such as word processors and database applications, did not need or benefit from a floating-point unit (FPU). Among the rare exceptions were CAD applications, which benefited immensely from a faster hardware FPU rather than slower software floating-point calculations. AMD had begun manufacturing its i386DX clone, the Am386, which was faster than Intel's. In response, Intel wanted to provide a lower cost i486 CPU for system integrators, but without sacrificing the better profit margins of a full i486. Intel accomplished this with the i486SX, the