Abstract: A method and system is provided for a computer system for testing base memory in which the computer system's operating system resides. The operating system is initially run out of the base memory in a first memory bank. A mapping scheme establishes a correspondence between physical addresses in the first memory bank and in a second memory bank, and logical addresses which map to the physical addresses in the first and second memory banks. The contents of the base memory from the first memory bank are copied to the second memory bank, and operation of the operating system from the base memory in the first memory bank is switched to the base memory copied into the second memory bank. After a memory test is performed on the first memory bank, the copied contents of the base memory are re-copied from the second memory bank back into the first memory bank, and operation of the operating system is switched back to the re-copied base memory in the first memory bank.