Abstract: A portion of microcode for a processor is stored outside the processor. If needed for execution, the processor loads the microcode from outside the processor into a microcode storage inside the processor. The microcode is loaded in the form of a microcode patch which consists of the microcode as well as other optional metadata and configuration data. The processor stalls and saves all instruction state prior to loading the microcode. Thus, the processor does not need to store all of the microcode inside the processor. The size of the microcode storage on the processor may be reduced.