M80C286

The M80C286 is an advanced, high-performance microprocessor with specially optimized capabilities for multiple user and multi-tasking systems. Depending on the application, a 10 MHz M80C286's performance is up to eight times faster than the standard 5 MHz M8086's, while providing complete upward software compatibility with Intel's M8086, 88, and 186 family of CPU's.

The M80C286 operates in two modes: M8086 real address mode and protected virtual address mode. Both modes execute a superset of the M8086 and 88 instruction set.

In M8086 real address mode programs use real addresses with up to one megabyte of address space. Programs use virtual addresses in protected virtual address mode, also called protected mode. In protected mode, the M80C286 CPU automatically maps 1 gigabyte of virtual addresses per task into a 16 megabyte real address space. This mode also provides memory protection to isolate the operating system and ensure privacy of each tasks' programs
and data. Both modes provide the same base instruction set, registers, and addressing modes.

The following Functional Description describes first, the base M80C286 architecture common to both modes, second, M8086 real address mode, and third, protected mode.