The RDMSR and WRMSR instructions the model-specific registers to be read or al written.
The model-specific registers are unique to the Pentium and are use o trace. check per formance, test, and check for machine errors. Both instructions use ECX to the register convey number to the microprocessor and use EDx:EAx for the 64-bit-wide read or write. Note that the register addresses are 0H-13H. See Table 18-5 for a list of the Pentium model-specific registers and their contents. As with the RDTSC instruction. these model-specific registers operate in the real or privilege level 0 of protected mode.