single or dual rail psu

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single or dual rail psu
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Chad Johnson
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December 19, 2009 - 9:54 pm
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Corsair is awesome. You'll never go wrong with a Corsair.

Single Rail v Double Rail? What do you plan to put in the computer with the power supply?

Ultimately it's not going to matter if you buy a high quality PSU, however.

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David Hartsock
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December 20, 2009 - 9:52 am
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To be honest... As long the the power supply has enough power (watts) to handle you components AND is a higher quality unit you won't have any problems.

Now the difference is that a dual rail supply has two sources for the same voltage. In theory if you have multiple devices pulling power off the same voltage rail (12v as an example) the power supply will be more stable as each rail supplies voltage to different components. In practice If you buy a power supply with plenty of power to begin with this won't be a problem because the instances where this would be an issue are extremely rare. There are many examples where a single rail PSU would be beneficial, and an an equal number where dual rail would be better. The key is to buy a power supply from a reliable company. If you plan on gaming and/or running some serious hardware then get a power supply that is rated much higher than the maximum amount of power that the components require - Think 650 watts. Stay with the higher quality brands - Corsair (as Ziggie said), Antec, OCZ, Cooler Master, Thermaltake, etc.

Dual rail has become a marketing term more than anything.

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David Hartsock
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December 20, 2009 - 6:35 pm
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Yes and no.

There are MANY generalizations in that statement that don't hold true for some designs, and are over stated for others.

[quote:2s6wlubo]A large, single 12-volt rail (without a 240VA limit) can transfer 100% of the 12-volt output from the PSU to the computer, while a multi-rail 12-volt design has distribution losses of up to 30% of the power supply's rating.[/quote:2s6wlubo]
30% loss in a power supply isn't abnormal, and yet they don't mention the losses in their design. Either way it is a generalization, since they don't provide specific schematics for the competitors circuits in question. BTW, there are losses in every electric circuit and losses in a power supply are generally larger than other circuits.

[quote:2s6wlubo]Those losses occur because power literally gets "trapped" on under-utilized rails.[/quote:2s6wlubo]
Trapped? More marketing talk. Unused power isn't "trapped".

[quote:2s6wlubo]...if the 12-volt rail that powers the CPU is rated for 17 amps and the CPU only uses 7A, the remaining 10A is unusable, since it is isolated from the rest of the system.[/quote:2s6wlubo]
That isn't necessarily a bad thing. There is actually a "safety" (my marketing term) factor in not using the entire amperage available. Components and wiring are less likely to be operating at there thermal limits.

The point is. Get a high quality power supply from a reputable manufacturer with a higher wattage than you will need. Look for one labeled "80 plus certified", which means that it is at least 80% efficient - very good by power supply standards. Everything else will be fine.

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David Hartsock
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December 21, 2009 - 6:20 pm
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That's a good choice!

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