Control Apparatus of Storage Unit, and Method of Controlling the Control Apparatus of Storage Unit

A method of controlling a control apparatus of a storage unit, a first communication port for communication with an external computer, a first processor that controls the first communication port, a first PCI-X bus, a first nonvolatile memory that the first processor accesses, a second communication port for communication with the external computer, a second processor that controls the second communication port, and a second PCI-X bus, the first processor executing a command stored in the first queue to control communication with the external computer, the second processor executing the command stored in the second queue to control communication with the external computer, the method comprising:

• causing the first processor to access and execute first commands stored in a first queue relating to communication between the external computer and the first communication port;
• causing the second processor to access and execute second commands stored in a second queue relating to communication between the external computer and the second communication port;
• causing the second processor to access and execute one of the first commands stored in the first queue;
• and
• changing at least a portion of a microprogram stored in the first nonvolatile memory while the second processor is being caused to implement the execution of said one of the first commands.