AMD-K6 Datasheet, PDF (300/346 Pages) Advanced Micro Devices – AMD-K6 Processor

AMD-K6^® Processor Data Sheet
Preliminary Information
20695H/0—March 1998
Table 59. Model-Specific Registers (MSRs)
Model-Specific Register
Value of ECX
Extended Feature Enable Register (EFER)
C000_0080h
SYSCALL/SYSRET Target Address Register (STAR) C000_0081h
For more information about the RDMSR and WRMSR
instructions, see the AMD K86™ Family BIOS and Software Tools
Development Guide, order# 21062.
Extended Feature Enable Register (EFER). T h e E x t e n d e d Fe a t u re
Enable Register (EFER) contains the control bits that enable
the extended features of the AMD-K6. Figure 102 shows the
format of the EFER register, and Table 60 defines the function
of each bit in the EFER register.
63
10
S
C
E
Symbol
Description
Bit
Reserved SCE System Call/Return Extension 0
Figure 102. Extended Feature Enable Register (EFER)
Table 60. Extended Feature Enable Register (EFER) Definition
Bit
Description
R/W
63–1 Reserved
R
0 System Call/Return Extension (SCE) R/W
SYSCALL/SYSRET Target Address Register (STAR).
The SYSCALL/SYSRET Target Address Register (STAR)
contains the target EIP address used by the SYSCALL
instruction and the 16-bit code and stack segment selector
bases used by the SYSCALL and SYSRET instructions. Figure
103 shows the format of the STAR register, and Table 61 defines
the function of each bit of the STAR register. For more
information, see the SYSCALL and SYSRET Instruction
Specification Application Note, order# 21086.
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Software Environment
Chapter 24