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Power Supply: Supermicro Knows Efficiency

Supermicro 5046A-XB: X58 Workstation Barebones
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Update:A reader recently brought up an interesting point about this PSU: if you like to power down your system when it's not in use, be aware that the fan in the server-oriented PWS-865-PQ continues spinning even after you shut down. If, instead, you let the workstation go into sleep mode, you won't have the supply's fan nagging at you. This wasn't an issue that factored into our review.

Focusing on power supply efficiency isn’t new to enthusiasts, but I’d argue that it is more of a novelty than in other market segments. In the server space, for instance, maximizing efficiency means that more AC power from the wall is converted to useful DC current and less is lost to heat. In a 42U rack populated with 1U servers sporting redundant power, the multiplicative effects are enormous. Even though Supermicro doesn’t do a ton of chest-thumping about its efficiency versus more mainstream vendors now achieving 80 PLUS certification, the company’s power supplies are some of the most efficient.

Case in point: the PWS-865-PQ that comes bundled with the SuperWorkstation is, as expected, 80 PLUS-certified. But Supermicro goes a step further and links straight to its certification report. As you can see, at light load, the PSU hits 80% efficiency. At what is considered a more typical 50% load (that's still high, as you'll see), efficiency jumps to 85%. And at full load, with 1,000+ input watts, efficiency dips to 83%.

The PWS-865-PQ is able to serve up to 70 A on its +12 V rail, which should be plenty for even the most powerful graphics configurations. The +5 and +3.3 V rails offer 30 A of current each.

Connectivity is plentiful. Because storage plugs straight into a backplane, you don’t really need to worry about available four-pin Molex connectors. Similarly, the 24-pin ATX and eight-pin auxiliary power connectors come plugged in already. You can tell the power supply was meant for servers because it sports a second eight-pin auxiliary plug, normally used in dual-processor configurations (and incidentally not compatible with PCIe 2.0 graphics cards requiring an eight-pin power input).

You get four six-pin PCIe connectors, which work well if you’re using a pair of Radeon HD 4870s, a single GeForce GTX 280 (with a 2 x six-pin to 1 x eight-pin adapter), but not so much if you want to use a pair of high-end cards requiring one eight- and one six-pin power plug each. The PWS-865-PQ simply wasn’t meant to support such a demanding pair of video cards. Hopefully, if you’re sticking to a single FirePro board or a couple of Quadro FXes, though, you won’t have a problem.

Check prices for Supermicro's 5046A-XB

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