An information processing apparatus for allowing a memory to be added thereto while being powered. The apparatus comprises a processor, a first main memory initially connected, and a connecting switch. The switch connects the processor, the first main memory, and a second main memory to be added. Main memory management information in the first main memory includes the size of memory resources connected to the processor. A storage region in the connecting switch retains information about whether or not the processor is connected to each of the memories. The setup allows the apparatus to use the added memory without having to be restarted.