The Unabridged Pentium 4 IA32 Processor Genealogy

Accessing the Code Segment

The processor accesses the code segment whenever it has to fetch an instruction from memory. Consider the following unconditional near jump instruction:

jmp 0009

The programmer has specified an offset, 0009h, within the current code segment as the target of this unconditional jump. In response, the processor compares the specified offset to the size, or limit, of the code segment currently in use to ensure that the programmer isn't attempting to jump outside the bounds of the current code segment. The code segment's start address, size and attributes are stored in the processor's internal CS cache register. If the target location is within the bounds of the segment, the processor adds the specified offset to the segment's ...