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

4-402 Vol. 2B
INSTRUCTION SET REFERENCE, N-Z
Operation
IF 64-BIt Mode and REX.W used
THEN
MSR[RCX] ← RDX:RAX;
ELSE IF (Non-64-Bit Modes or Default 64-Bit Mode)
MSR[ECX] ← EDX:EAX; FI;
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.
If the value in EDX:EAX sets bits that are reserved in the MSR
specified by ECX.
Real-Address Mode Exceptions
#GP(0) If the value in ECX specifies a reserved or unimplemented MSR
address.
If the value in EDX:EAX sets bits that are reserved in the MSR
specified by ECX.
Virtual-8086 Mode Exceptions
#GP(0) The WRMSR instruction is not recognized in virtual-8086 mode.
Compatibility Mode Exceptions
Same exceptions as in Protected Mode.
64-Bit Mode Exceptions
Same exceptions as in Protected Mode.