Intel 64 and IA-32 Architectures Software Developers Manual Volume 2B, Instruction Set Reference, N-Z

4-240 Vol. 2B
INSTRUCTION SET REFERENCE, N-Z
Operation
IF 64-Bit Mode and REX.W used
THEN
RAX[31:0] ← MSR(RCX)[31:0];
RAX[63:32] ← 0];
RDX[31:0] ← MSR(RCX)[63:32];
RDX[63:32] ← 0];
ELSE
(* Non-64-bit modes, 64-bit mode default *)
EDX-EAX ← MSR[ECX];
FI;
Flags Affected
None.
Protected Mode Exceptions
#GP(0) If the current privilege level is not 0.
If the value in ECX specifies a reserved or unimplemented MSR
address.
Real-Address Mode Exceptions
#GP If the value in ECX specifies a reserved or unimplemented MSR
address.
Virtual-8086 Mode Exceptions
#GP(0) The RDMSR instruction is not recognized in virtual-8086 mode.
Compatibility Mode Exceptions
Same exceptions as in Protected Mode.
64-Bit Mode Exceptions
#GP(0) If the current privilege level is not 0.
If the value in ECX or RCX specifies a reserved or unimple-
mented MSR address.