Verdict: Meet the world's most powerful PSUs
Although a true 500W PSU will provide enough power for high-end PCs, if you're planning on building a really high-end system with multiple graphics cards and lots of disk drives then a more powerful PSU will almost certainly be required. Throw an overclocked dual-core or dual-CPU setup into the mix, and 500W begins to look decidedly weedy.
The first two 1kW PSUs to appear are the Enermax Galaxy EGA1000EWL and the Tagan TurboJet TG1100-U95. Enermax claims that the EGA1000EWL can output 1kW, while Tagan claims that the TG1100-U95 can output 1.1kW.
Unlike other high-wattage PSUs that comprise several small PSUs working together in parallel, the Enermax is based on a single custom-built PCB. Theoretically, this means that it should be more efficient than other parallel-design PSUs and, as a result, should output less waste heat. The guts are kept cool by a 135mm fan that sucks in air from the bottom, which is then expelled by an 80mm fan at the rear. With three transformers, the Enermax has a whopping five 12V rails, each rated as capable of outputting 17A, up to a combined maximum to 900W, plus the usual complement of less powerful 3.3V, 5V, -12V and 5VSB rails.
The arrangement of these rails is clever, and is designed as follows: 12V1 and 12V2 rails supply the two 4-pin ATX12V and the single 8-pin EPS12V plug, 12V3 supplies the motherboard, second PCI-E and S-ATA plugs, and 12V4 serves the master PCI-E and Molex plugs. The 12V5 rail rounds off the charge by supplying power to all of the modular plugs. This is a good arrangement, as it means that power-hungry graphics cards won't interfere with the CPU(s) or motherboard, since they're all powered by separate rails.
The Enermax has more connections than a Mafia godfather, including support for a theoretical maximum of 24 drives. Fortunately, if your PC doesn't have that many drives, it doesn't have to be buried in a nest of cables, as more than half of the EGA1000EWL's connections are provided on modular cables. This makes it far easier to build a tidier, and therefore cooler, PC with the Enermax than with the Tagan, which only has hard-wired connections. The only downside to the Enermax is that it's considerably longer than most PSUs. However, if you intend to buy a 1kW PSU then you'll probably have an enormous PC case anyway.
In contrast to the Enermax, the Tagan is a more traditional design. Although it has a total combined output of 1.1kW, it has only four 12V rails. This means that although each 12V rail is rated as being capable of supplying 20A, because it has fewer rails than the Enermax, there's some overlap. For example, the Tagan's 12V2 supplies power to the motherboard, plus the 4-pin ATX12V and 8-pin EPS12V CPU plugs, which may cause problems if you overvolt either component. The 12V1 rail supplies juice to the Molex and S-ATA plugs, 12V3 powers the first and third PCI-E plugs, with 12V4 powering the second and fourth PCI-E plugs. The interior of the Tagan is kept cool by two temperature-controlled 80mm fans, one at the front and one at the rear.
As mentioned earlier, the plugs on the Tagan are hard-wired, so regardless of how many components are in your PC, the inside of your case will end up looking like spaghetti junction. All of the connectors you'd expect to find are present, including four PCI-E, and both 4-pin ATX12V and 8-pin EPS12V plugs. Strangely, the ATX connector is compatible with both 24- and 20-pin motherboards, although we doubt that older PCs with 20-pin motherboards would need a 1.1kW PSU.
PERFORMANCE
Previously, we had to test PSUs in Maxpoint's lab in Germany. More recently, though, Enermax brought some testing equipment to the UK and offered us the chance to use it. This means that we'll be able to review PSUs more regularly, rather than in just one Labs test each year. Although the new test equipment is different from the setup we used in Germany, the Chroma 6310 is another off-the-shelf, industry-standard DC load programmer, so we have total confidence in its test results.
We test PSUs by programming the load tester to drain the number of amps claimed by the manufacturer from each of the PSU's rails, starting at 50 per cent of this value, then moving up to 75 per cent, and finally, 100 per cent load. We also run a stress test by running the PSU at 100 per cent load for an hour. We then measure the output in volts from each rail to check whether it's within the limits set by the industry-standard ATX spec. If the voltage is above or below the limit stipulated by the ATX spec then it may damage your components, or cause the PC to shut down, so this is counted as a fail.
Both the Enermax and Tagan passed these voltage stability tests with flying colours. However, the Tagan became very hot during testing, and its temperature-controlled fans sped up to a noisy level. In contrast, the Enermax ran much cooler and far quieter, creating no more noise than we've heard from a decent 600W PSU. This is no doubt partly due to the Enermax's greater efficiency; it averaged 82 per cent efficiency at full load, compared to 79 per cent for the Tagan.
CONCLUSION
Although both monster PSUs proved to be 100 per cent stable, it's important to note that there's a huge difference between them as regards design philosophy. The TG1100-U95 has just four 12V rails, so there's some overlap in its power distribution, while its two 80mm fans spin quickly and noisily to keep it cool. This is because Tagan has squeezed a 1.1kW design into a case that's too small, leaving barely any room for air to pass through the crowded interior. In fact, the outer case of the Tagan became almost too hot to touch, which is a serious issue, as this heat will be conducted into your PC case through the PSU's contact with the case. As a result, the Tagan's temperature-controlled fans spin up to maximum speed at anything above 75 per cent load, making it sound like a squadron of RAF Chinook heavy-lift helicopters.
In contrast, the Enermax runs much cooler and quieter thanks to its bigger dimensions and larger fans. More importantly, it distributes its power evenly across five 12V rails. The modular cables also mean that it's easier to build a tidy PC using it. Of the 1kW PSUs we've seen, the efficient, cool-running and quiet Enermax Galaxy is the clear winner.
