AMD Geode LX 800@0.9W - Manual (Page 653)

AMD Geode™ LX Processors Data Book 653
Instruction Set 33234H
Notes
The RSM instruction does not check the values that it reads from the SMM header for validity.
The RSM instruction set the current privilege level to the SS DPL value read from the SMM header.
If a RSM restores the processor to real mode, the VM bit of the EFlags register is cleared regardless of the state of the VM
bit in the EFlags value of the SMM header.
If RSM restores the processor to a privilege level that is not 3, then the VM bit of the EFlags register is cleared, regardless
of the contents of the VM bit in the EFlags value of the SMM header.
8.3.4.8 RSTS - Restore Task Register and Descriptor
Operation
Description
Restore the Task register and descriptor from memory. Below is the format of the descriptor contents in memory.
Flags Affected
None.
Exceptions
#UD If current privilege level is not 0, or the SMM_INST_EN = 0 and if the processor is not in SMM and if the processor
is not in DMM.
Notes
The reg field within the mod r/m byte must be zero for the RSTS instruction to be recognized.
The RSTS instruction does not check its memory operand for validity. Care should be taken to always load valid data into
the TS.
8.3.4.9 SETALC - Set AL to CF
Operation
AL <= {8{CF}};
Description
IF the EFlags CF is set, then the SETALC instruction sets AL to FFh. Otherwise, SETALC sets AL to FFh.
Flags Affected
None.
Opcode Instruction Clocks Description
0F 7D RSTS m80 12 Restore TS from memory
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
SELECTOR[15:3] TI RPL +8
BASE[31:24] G B 0 V LIMIT[19:16] 1 DPL 1 0 E W A BASE[23:16] +4
BASE[15:0] LIMIT[15:0] +0
Opcode Instruction Clocks Description
d6 SETALC 2 Set AL according to CF.
IF (CPL<>0 OR (SMM_INST_EN=0 AND SMM=0 AND DMM=0))
#UD;
ELSE
TS.DESCR <= MEM80;