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

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Memory Addressing

General

The 8088/8086/286 processors contained a set of four segment registers—CS, DS, ES, and SS. The 386 processor contains a set of six segment registers—CS, DS, ES, FS, GS, and SS. In Real Mode, the programmer uses these registers to specify the start address of up to six different areas of memory space to be utilized by the currently executing program as data, code and stack areas. Figure 5-20 on page 71 illustrates the segment registers.

Figure 5-20. Segment Registers

Each of the segment registers is only 16 bits in size. When the programmer loads a value into one of these registers in Real Mode, the processor automatically ...

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