The value in ECX specifies one of the 64-bit Model Specific Registers of the Pentium processor. The content of that Model-Specific Register is copied into EDX:EAX. EDX is loaded with the high-order 32 bits, and EAX is loaded with the low-order 32 bits.
The following values are used to select model specific registers on the Pentium processor.
┌─────┬──────────────────────┬──────────────────────────────────────────────┐ │VALUE│REGISTER NAME │DESCRIPTION │ ├─────┼──────────────────────┼──────────────────────────────────────────────┤ │ 00H │Machine Check Address │Stores address of cycle causing the exception │ ├─────┼──────────────────────┼──────────────────────────────────────────────┤ │ 01H │Machine Check Type │Stores type of cycle causing the exception │ └─────┴──────────────────────┴──────────────────────────────────────────────┘
For other values used to perform cache, TLB, and BTB testing and performance monitoring, see the Intel documentation.