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112 AMD Geode™ LX Processors Data Book
CPU Core Register Descriptions
33234H
5.5.2.4 SYSENTER/SYSEXIT Code Segment Selector MSR (SYS_CS_MSR)
SYS_CS_MSR is used by the SYSENTER instruction (fast system call) as the selector of the most privileged code seg-
ment. SYS_CS plus 8 is used by SYSENTER as the selector of the most privileged stack segment. SYS_CS plus 16 is
used by SYSEXIT as the selector of the least privileged code segment. SYS_CS plus 24 is used by SYSEXIT as the selec-
tor of the least privileged stack segment.
MSR Address 00000174h
Typ e R /W
Reset Value 00000000_C09B0000h
SYS_CS_MSR Register Map
63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32
RSVD
313029282726252423222120191817161514131211109876543210
G D RSVD P DPL S X C R A CS_SEL TI RPL
SYS_CS_MSR Bit Descriptions
Bit Name Description
63:32 RSVD Reserved.
31 G (RO) Granularity (Read Only). Code segment limit granularity is 4 KB. (Default = 1)
30 D (RO) Default (Read Only). Code segment default size is 32 bits. (Default = 1)
29:24 RSVD (RO) Reserved (Read Only).
23 P (RO) Present (Read Only). Code segment descriptor is present. (Default = 1)
22:21 DPL (RO) Descriptor Privilege Level (Read Only). Code segment descriptor privilege level.
(Default = 11)
20 S (RO) Segment (Read Only). Code segment is not a system segment. (Default = 1)
19 X (RO) Executable (Read Only). Code segment is executable. (Default = 1)
18 C (RO) Conforming (Read Only). Code segment is conforming. (Default = 0)
17 R (RO) Readable (Read Only). Code segment is readable. (Default = 1)
16 A (RO) Accessed (Read Only). Code segment was accessed. (Default = 1)
15:3 CS_SEL Code Segment Selector. (Default = 0)
2TI Descriptor Table Indicator. (Default = 0)
1:0 RPL (RO) Requestor Privilege Level (Read Only). (Default = 0)