Architecture

Architecture


The processor was a significant evolution in a long line of processors that stretched back to the Intel 8008. The predecessor of the 80386 was the Intel 80286, a 16-bit processor with a segment-based memory management and protection system. The 80386 added a 32-bit architecture and a paging translation unit, which made it much easier to implement operating systems which used virtual memory. It also has hardware debugging support.

The 80386 featured three operating modes: real mode, protected mode and virtual mode. The protected mode which debuted in the 286 was extended to allow the 386 to address up to 4 GB of memory. The all new virtual 8086 mode (or VM86) made it possible to run one or more real mode programs in a protected environment.

Though Intel would shortly introduce the 80486 and eventually the Intel Pentium line of processors, the support in the 386 for the 32-bit flat memory model would arguably be the most important feature change for the x86 processor family until AMD released x86-64 in 2003.

Chief architect in the development of the 80386 was John H. Crawford[3]. He was responsible for the 32-bit extension of the 80286 architecture and instruction set, and then lead the microprogram development for the 80386 chip.