in a computer system having a processor , a system memory , a flash memory , and a memory controller , a method comprising the steps of loading a flash memory upgrade program containing a new flash memory image and a digital signature into a portion of the system memory ; configuring the memory controller to limit the processor to accessing only the flash memory and the portion of the system memory ; verifying the flash memory update program using the digital signature ; and , updating the flash memory only if the flash memory upgrade program is authentic .