This document details the procedure for performing microcode updates on the AMD K8 processors. It also gives background information on the K8 microcode design and provides information on altering the microcode and loading the altered update for those who are interested in microcode hacking. Surprisingly, the microcode itself is in no way encrypted as it is in Intel microcode updates; the raw data loaded into the microcode patch array is directly exposed. The repetitive structure of the data, bit patterns and fields characteristic of microcode indicate that apparently no encryption was performed.