Articles: Cases/PSU

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Like the previous PSU-related test session on our site, this one is about high-wattage power supplies, typically selling independently of system cases (the only exception is the Macropower MP360AR ver.2; you can meet it outside the system case, but it will be an OEM version, without the colorful box, installation guide and other nice trifles). Two out the tested seven products present the highest interest: the models from A.C. Ryan and OCZ Technology allow removing or installing their output connectors as necessary, thus freeing your computer from unneeded cables which can be a big nuisance in small system cases.

But before getting to the tests, I want to clarify a few theoretical points that provoked questions from the readers of my previous articles. They concern the new 24-pin power connector on mainboards, PSUs with two +12V outputs, and the efficiency factor of power supplies.

As you know, the latest generations of graphics cards exhibit a very healthy appetite for power. They easily consume up to 60-70 watts, while the AGP slot cannot yield more than 40 watts, as stated in its specification. So, they started to put additional power connectors on top graphics card models; the connector was of the Molex type at first and then of a special 6-pin variety. The PCI Express slot that is now steadily replacing AGP permits consumption of up to 75 watts, so many PCI Express-compliant graphics cards don’t need an additional power connector on board. But when you use such a card, the mainboard’s power connector – already heavily loaded – becomes the weak spot.

Moreover, modern graphics cards consume ever more power from the +12V rail, and there’s only one pin in the mainboard’s power connector for this voltage. As a result, this pin sometimes overheats and gets burned out with the ensuing consequences for the whole system. As a way to solve this problem, mainboards with PCI Express now come with a new 24-pin power connector (incidentally, it is exactly the same as the EPS connector employed in power supplies for servers) instead of the older 20-pin one. The four added pins are “ground”, +5V, +12V and +3.3V and this allows to power up PCI Express graphics cards without any problems. You can regard the new connector as the old one with four new pins attached to its side, that’s why new mainboards are compatible with older power supplies and vice versa: the new pins of the connector are just left open in this case.

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