Abstract: A test system for functionally testing disk drives over a wide range of power conditions. The system simulates the power conditions using a computer controlled system architecture featuring several major components. The first of these components is a computer enhanced with features allowing the computer to communicate with disk drives having either IDE or Small Computer System Interface (SCSI) formats. The computer communicates with a second component termed the programmable power supply (PPS) and a third component having simulation circuitry termed universal power simulator, or UPS. The computer uses a combination of hardware and software to create simulated power conditions which are used to test the disk drives for correct operation and to glean out defective drives. The UPS is responsive to control signals from the host computer and the PPS and sends simulated power signals to the disk drives under test.