Microcode upgrade and special function support by executing risc instruction to invoke resident microcode

Abstract

A method and apparatus for invoking microcode instructions resident on a processor by executing a special RISC instruction on the processor such that special functions are provided. In one embodiment, the special function invoked may be a feature of the processor not included in the processor's publicly known instruction set. In another embodiment, the special function invoked may cause a set of instructions to be transferred from a memory external to the processor to a memory in the processor. In such an embodiment, the method and apparatus include authenticating and decrypting the instructions before transferring from the memory external to the processor to the memory in the processor. In such an embodiment, the method and apparatus may be used for upgrading microcode within a processor by executing the special RISC instruction stored on a writeable non-volatile memory located external to the processor. In this embodiment, executing the special RISC instruction invokes resident microcode instructions on the processor to transfer microcode instructions from a memory located external to the processor to memory in the processor so that the microcode upgrade is executed in place of and/or in addition to other microcode resident in the processor. In yet another embodiment, the special RISC instruction could cause instructions to be transferred from a memory external to the processor to be transferred to the processor, decrypted, authenticated and then executed in the processor securely, privately, and without interruption.