M80C286 High Performance CHMOS Microprocessor with Memory Management and Protection

The M80C286 is an advanced 16 bit CHMOS III microprocessor designed for multi-user and multitasking applications that require low power and high performance. The M80C286 is fully compatible with its predecessor the HMOS M80286 and object-code compatible with the M8086 and M80386 family of products. In addition, the M80C286 has a power down mode which uses less power, making it ideal for mobile applications. The M80C286 has built-in memory protection that maintains a four level protection mechanism for task isolation, a hardware task switching facility and memory management capabilities that map 2 30 bytes (one gigabyte) of virtual address space per task (per user) into 2 24 bytes (16 megabytes) of physical memory.

The M80C286 is upward compatible with M8086 and M8088 software. Using M8086 real address mode, the M80C286 is object code compatible with existing M8086, M8088 software. In protected virtual address mode, the M80C286 is source code compatible with M8086, M8088 software which may require upgrading to use virtual addresses supported by the M80C286's integrated memory management and protection mechanism. Both modes operate at full M80C286 performance and execute a superset of the M8086 and M8088 instructions.

The M80C286 provides special operations to support the efficient implementation and execution of operating systems. For example, one instruction can end execution of one task, save its state, switch to a new task, load its state, and start execution of the new task. The M80C286 also supports virtual memory systems by providing a segment-not-present exception and restartable instructions.

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