Method and apparatus for securing computer firmware wherein unlocking of nonvolatile memory is prohibited unless address line masking Is disabled during an initialization event

摘要

A method and apparatus for initializing a computer system, which includes a lockable nonvolatile memory coupled to a processor having maskable address lines and a cache, when a nonvolatile memory update is in process. When an update is in process, the nonvolatile memory is unlocked in response to the initialization event only if address line masking is disabled, and at least a portion of the processor cache is invalidated to ensure the processor will fetch the first instruction from the nonvolatile memory.