Test System and Performance Analysis
Test Configuration: Testing a PSU at peak output can be difficult with units of this size. Test equipment designed specifically for this task is available, but it doesn't come cheap. Instead, we attempted to set up a power hungry test machine with a fair collection of components for adequate power demands, simulating real-world conditions. We overclocked the CPU and Video Cards for increased power demands as well, and raised all voltages to their maximum via the system BIOS. Once set, we launched a Torture Test in Prime95 to maximize CPU usage, then ran an X3: Reunion benchmark at 1600x1200 at 8xS Anti-Aliasing and 16X Anisotropic Filtering to add further demands to the system. While this still could not cause a peak draw on either PSU, the load was enough to bring our 550 Watt comparison PSU down. To start, all metrics were record at IDLE, where the system was left to sit for 20 minutes before recording the various statistics, then the readings were recorded again under load.
Tagan Turbojet TG1100-U95
Thermaltake Toughpower 750 W Cable Management
Ultra X2-Connect - 550W
nForce4 SLIX16 chipset
GeForce 7900 GT (x2)
Overclocked from 627/820 to 725/900
Ageia PhysX 128MB
1 - 400GB Seagate Barracuda
1 - 250GB Maxtor 7Y250M0
1 - Sony DW-Q120A 16X DL DVD +/-R/RW
1 - Sony CRX320EE 52x32x52/16X Combo
P4400 KILL A WATT Meter
X3: Reunion Demo (Max Settings)
Prime95 (Torture Test)
In each test, we can see that the AC input had minor fluctuations, but essentially remained steady throughout testing. At idle speeds, the Thermaltake Toughpower 750W drew the least amount of wattage of the three units, as well as when under load. The Thermaltake Toughpower 750W delivered 11.84V idle, which is within +/-3% limits, while dropping slightly to 11.74V with peak wattage reaching 537 watts. With the Tagan Turbojet TG1100-U95 drawing a peak 558 Watts, the 12V rails compensated for the demand, increasing slightly over output when idle. We should also note that the Tagan Turbojet TG1100-U95 was the only unit of the three to actually provide 12V or higher during testing. The UltraX2 Connect 550 took the biggest performance hit on the 12V rail, however, this was the only PSU where we were able to overshoot its peak wattage, triggering the overload circuit several times during testing. When we look at the 5V and 3.3V outputs, all three PSUs tested were relatively steady across the board. Once again, the Tagan Turbojet TG1100-U95 was the only one of the three to exceed rated output, delivering a minimum of 3.41V and 5.19V respectively.
The last reading we calculated was each PSU's Power Factor. The Power Factor is calculated by dividing true power (Watts) by apparent power (VA). This ultimately represents each PSU's efficiency at converting actual current to the load power with a Power Factor of 1 being most efficient and a Power Factor 0 being the least efficient. So, for example, if a PSU has a Power Factor of 1, this means the PSU is applying 100% of the actual power to the load side. A Power Factor of .50 indicates a PSU is able to take the actual current and apply 50% percent to the load. So, when we look at all three PSUs above, we find that both the Tagan and Thermaltake models are very efficient, with a Power Factor of .99, whereas the UltraX2 is less efficient with a Power Factor of .65/.66. Please note, this is an overly simplistic explanation to a complex technical term. For a complete explanation of the Power Factor, we'd suggest reading this application note article from ST Microelectronics.