The Intel 80386 is a 32-bit microprocessor that helped to launch the Windows era. Thanks to its incorporation of advanced memory management circuitry, the enables programs to switch from real mode to protected mode without rebooting; in short, they made protected- mode operating systems and applications possible for the first time.
The chip’s 32-bit address bus lets it manage as much as 4GB of random access memory (RAM) and 64TB of virtual memory. Various versions of the 80386 run at clock speeds of 16 MHz, 20 MHz, 25 MHz, and 33 MHz. Introduced in 1985, the 80386 was renamed the Intel 386DX when the Intel 386SX.