AMD-K6 AMD [Advanced Micro Devices], AMD-K6 Datasheet - Page 217

• Manufacturer Part Number: AMD-K6
• Description: AMD-K6 Processor
• Manufacturer: AMD [Advanced Micro Devices]

20695H/0—March 1998
10.5
10.6
Chapter 10
SMM Base Address
Halt Restart Slot
Table 35. SMM Revision Identifier
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.
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.
Reserved
31–18
0
System Management Mode (SMM)
SMM Base Relocation
17
1
I/O Trap Extension
16
1
AMD-K6
®
SMM Revision Level
Processor Data Sheet
0002h
15–0
199