Taming Intel’s “Brain Damaged” Chip

The first generation of Intel’s 16-bit microprocessors turned out to be a surprising success after IBM chose their 8088 model for the IBM PC computer.Many software industry leaders expected the transition from 8-bit to 16-bit computing to bring more capable operating systems, including multitasking and networking support. That did not happen: the IBM PC shipped with a clone of the old, single-tasking CP/M operating system, called PC DOS and most of the industry followed.In early 1982, Intel announced the next generation of its x86 processors, the 80286, and there was hope the operating systems would finally catch up. That did not happen either.Two Modes of OperationThe 80286 could be run in one of the two modes: Real Address Mode or Protected Virtual Address Mode1 . Real Address Mode, usually called “Real Mode” was a compatibility feature. The CPU would start in Real Mode and would be able to run software written for the 8086 architecture without any modifications. Strictly speaking,…