When it comes to testing a power supply, there are two courses to travel. One takes you down a path using a device to stress out the PSU and provide data regarding the power levels across all three rails. The second, and the one I make use of, utilizes an actual test system to give a more real-world account of what the power supply is capable of. While both methods have their merits, I prefer to use an actual computer to more closely resemble the manner of use that you, the potential customer, will put the product through.
That said, let's take a quick look at the test system. I have continued to beef up the system to put a more realistic strain on the power supply.
MSI X48C Platinum motherboard (Supplied by MSI)
Intel Core 2 Duo E6600 processor
2x 1024MB Corsair XMS2-8500-C5 memory (Supplied by Corsair)
2x Sapphire X2900XT graphics boards in CrossfireX configuration (Supplied by Sapphire)
Western Digital 250GB SATA hard drive
2x Western Digital 160GB SATA hard drives
Western Digital 80GB hard drive
Sony 52x CD-ROM optical drive
Samsung 16x DVD-R optical drive
1x 200mm fan
2x 120mm fans
While this isn't a Quad-GPU setup, we are certainly in the realm of having a system that is going to put a significant power drain on any power supply. Each of the X2900XT boards is capable of pulling close to 250 watts of power. Testing will consist of checking the power levels across all three rails at idle and again while the system is under stress. This should give us a good look at the capabilities of the power supply being tested.
The voltage levels dropped very little during our testing phase, but this was expected. Most high-end power supplies are designed to handle the rigors of a hefty 12v set of components and the Topower PowerBird 1100 doesn't miss the mark. While testing the system under a load, I also monitored the power rails for any fluctuation of voltage level. Both the 3.3v rail and the 12v rail displayed a strict output of the recorded voltage. The 5v rail had a slight fluctuation of 0.01v, so was not anything that would cause concern. Overall the power supply performed very well with the ability to take a pair of power hungry video boards and handle their needs with ease.