The 386 Register Set

Figure 5-3 on page 45 illustrates the 386's register set. The following subsections provide a brief introduction to these registers and a detailed description of each of them can be found later in the book.

Figure 5-3. 386 Register Set

Control Registers

CR0

32 bits wide. Refer to Figure 5-4 on page 47 and Table 5-2 on page 46. CR0 in the 386 permitted the OS:

  • To control whether or not the processor is operating in Real or Protected Mode.

  • Assuming that the processor is in Protected Mode, to control whether or not Paging is enabled.

  • To discover whether or not a FPU is present.

  • Assuming that a x87 FPU coprocessor was present on ...

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