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The Unabridged Pentium 4 IA32 Processor Genealogy by Bob Colwell, Tom Shanley

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Soft Reset (INIT#)

The Pentium® was the first IA32 processor to implement the INIT# (Initialization) input pin. This is effectively a soft reset to the processor.

Hot Reset and 286 DOS Extender Programs

MS-DOS was written specifically for the 8088 processor using 8088-specific instructions. Since the 8088 only implemented 20 address signal pins, it was incapable of generating a memory address greater than FFFFFh, or 1MB. Furthermore, Protected Mode wasn't introduced until the advent of the 286 processor. Consequently, MS-DOS could only address the lower 1MB and had no concept of Protected Mode.

When a 286 was powered up, it initially operated in Real Mode. In other words, it operated as if it were an 8088. Among other things this meant that, ...

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