Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Model-specific registers (MSRs) are control registers provided by processor implementations to provide system software with features that are provided on specific processor implementations, but not others. MSRs are used for performance monitoring, debugging, testability and program ...Full description
Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Model-specific registers (MSRs) are control registers provided by processor implementations to provide system software with features that are provided on specific processor implementations, but not others. MSRs are used for performance monitoring, debugging, testability and program execution tracing, but also to enable and disable certain model-specific features of the processor implementation. For example, on the AMD K6 and later and most other newer processors (including all processors implementing AMD64 architecture), the individual bits of the EFER (Extended Feature Enable Register) configure whether the SYSCALL and SYSRET instructions are available, whether long mode can be activated and is active and if the no-execute page-protection feature is enabled.