AMD AMD-K6-2/400 User Guide - Page 268
SMM Base Address, 12.5 Halt Restart Slot, Table 47., SMM Revision Identifier
View all AMD AMD-K6-2/400 manuals
Add to My Manuals
Save this manual to your list of manuals |
Page 268 highlights
Preliminary Information AMD-K6™-2E+ Embedded Processor Data Sheet 23542A/0-September 2000 12.4 12.5 246 Table 47 shows the format of the SMM Revision Identifier. Table 47. SMM Revision Identifier 31-18 Reserved 0 17 SMM Base Relocation 1 16 I/O Trap Extension 1 15-0 SMM Revision Level 0002h SMM Base Address During RESET, the processor sets the base address of the code-segment (CS) for the SMM memory area-the SMM base address-to its default, 0003_0000h. The SMM base address at offset FEF8h in the SMM state-save area can be changed by the SMM service routine to any address that is aligned to a 32-Kbyte boundary. (Locations not aligned to a 32-Kbyte boundary cause the processor to enter the Shutdown state when executing the RSM instruction.) In some operating environments it may be desirable to relocate the 64-Kbyte SMM memory area to a high memory area in order to provide more low memory for legacy software. During system initialization, the base of the 64-Kbyte SMM memory area is relocated by the BIOS. To relocate the SMM base address, the system enters the SMM handler at the default address. This handler changes the SMM base address location in the SMM state-save area, copies the SMM handler to the new location, and exits SMM. The next time SMM is entered, the processor saves its state at the new base address. This new address is used for every SMM entry until the SMM base address in the SMM state-save area is changed or a hardware reset occurs. Halt Restart Slot During entry into SMM, the halt restart slot at offset FF02h in the SMM state-save area indicates if SMM was entered from the Halt state. Before returning from SMM, the halt restart slot (offset FF02h) can be written to by the SMM service routine to specify whether the return from SMM takes the processor back to the Halt state or to the next instruction after the HLT instruction. System Management Mode (SMM) Chapter 12