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7-15
SYSTEM MANAGEMENT MODE
The programmer should not modify the contents of this area in SMRAM space directly. SMRAM
space is reserved for CPU access only and is intended to be used only when the processor is in
SMM.
7.3.5 Resume Instruction (RSM)
After an SMI# request is serviced, the RSM instruction must be executed to allow the CPU to
return to an application transparently after servicing the SMI#. When the RSM instruction is ex-
ecuted, it restores the CPU state from SMRAM and passes control back to the operating system.
The RSM instruction uses the special opcode of 0FAAH. The RSM instruction is reserved for the
SMI# handler and should only be executed by the SMI# handler. Any attempt to execute the RSM
outside of SMM mode results in an invalid opcode exception. At the end of the RSM instruction,
the processor drives SMIACT# high, indicating the end of an SMM routine.
7.4 THE Intel386 EX PROCESSOR IDENTIFIER REGISTERS
The processor has two identifier registers: the Component and Revision ID register and the SMM
Revision ID register. The component ID is 23H; the component revision ID is 09H. This register
can be read as 2309H. The SMM revision identifier is 10000H.