Updates in a Multiprocessor System

A multiprocessor system incorporates two or more processors. The system designers may choose to enforce a policy wherein all of the processors must be of the same type and stepping. In this case, it would only be necessary for the BIOS to incorporate a single update image appropriate to the supported processor stepping. The loader program must be executed by each processor and must verify, via the CPUID instruction, that the update is appropriate to the processor stepping before loading it. It must then load the update into the processor, after which it must authenticate that the load was successful (by checking the signature).

On the other hand, the system designers may allow the processors to be of different steppings. In this case, the system BIOS must incorporate multiple update images, one for each of the supported processor steppings. The loader must be executed by each processor and must obtain, via the CPUID instruction, the processor's stepping information. It must then locate and load the update appropriate to the processor, after which it must authenticate that the load was successful.

Since the procedure used to initialize a multiprocessor system (see “BSP Selection Process” on page 1595) must verify the existence of all of the system's processors, it would be practical to include the update load process into this procedure.