An apparatus and a method for testing memory of a computing device, and more specifically to testing a Central Processing Unit (CPU), a system memory, and a combination thereof. The computing system includes one or more CPUs, a system memory, input and output devices. Among other features, the apparatus and method described herein can remove either a defective CPU or a defective portion of system memory from the computing device. An exemplary apparatus and method also reports to a computer user whether any CPU or system memory is defective as well as specifically identifying the defective computing component. The apparatus and method also detects a first defect related to a first corrupted portion of an instruction of a test program code and a second defect related to a second corrupted portion of the instruction.