In a state of a system in which a processor of the system is not accessing a first memory, a controller in the system determines whether system boot code from the first memory in the system is compromised, wherein the first memory is accessible by the processor and the controller over a bus. In response to determining that the system boot code is compromised, the controller retrieves system boot code from a second memory in the computing device to replace the system boot code in the first memory, where the second memory is electrically isolated from the bus and is inaccessible by the processor.