Abstract: A programmable firmware store for a personal computer system includes a plurality of nonvolatile alterable electronic memories connected in a mutually paralleled circuit arrangement. The memories are connected to a controller that controls the memories to read firmware from and write firmware into the electronic memories, and to write-protect at least one of the memories. Any memory can be write-protected as initially selected by a user or technician of the system. The initial selection can be changed easily to write-protect another of the memories. The firmware in one memory includes code for checking the validity of firmware stored in another memory, and for selecting one or the other of the memories dependent upon a version code of the firmware. The controller also includes an update code for updating the firmware in a selected memory.