It's all very well upgrading your graphics card, but your PC also needs enough power to ensure it can deliver the superior video-handling you expect. PC Advisor explains the crucial role of the PSU and tests five powerful units.
How we test
The PC Advisor Test Centre upped sticks to FSP's testing facility in St Albans for the purpose of this group test. Using a Chroma 61604 programmable 230V AC power source and a bank of Chroma 63103 load modules, we were able to precisely measure the amount of mains power supplied first to the PSUs, and then from the PSU to the PC.
The PSUs were connected to the bank of load modules via a board filled with typical PC power connectors. The load modules were able to simulate the power requirements of various computer components, and their controls allowed us to select the precise power load we wanted to place on the PSU.
We set up the load modules to simulate the power requirements of four hypothetical PCs: the first drawing 350W, the second 700W, the third 750W and, finally, 800W. We tested the PSUs under each of these scenarios, starting with the lightest and finishing with the heaviest load.
For each of these tests, we were able to calculate the efficiency of any given PSU by comparing the power it drew from the AC source with the amount of power that it delivered to the PC. The perfect PSU should be able to convert 100 percent of the power drawn from the AC source into useful PC power but, in a real-world scenario, 80 percent efficiency is a good result.
A PSU needs to be able to provide power at three voltages: 12V, 5V and 3.3V. As the PSU reaches the limit of its capabilities, these voltages can start to tail off. Some tolerance is allowed, but the closer it keeps to your various components' specifications, the better your chances of having a smooth-running PC. If these voltages drop too far, your PC components will receive inadequate power, causing crashes and system failures.
Although the PSUs in this group test have various power ratings from 700W up to 780W, we tested each of them at 800W to see how well they coped with increasing loads. None of the PSUs failed or exploded during testing, which is one possible outcome of such an overload.
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