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OCZ Modxstream 700w - SLI GTX 460s

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October 18, 2011 10:52:18 PM

Power consumption isn't my strong suit and I don't quite understand two 12v rails @ 25 Amps (which this PSU is) vs a different PSU that has one rail and more amps...so here goes.

Will this work? SLI GTX 460s 1GB with the OCZ Modxstream 700w PSU. Sure, I know it's safer to go bigger and better, but this is currently what I have. I've seen at full load that dual GTX 460s will use about 433W. Regarding the rest of the system, how much would a standard machine pull? I'll have an i5-2500k that will be overclocked, but nothing extreme. 1 HD, maybe an SSD, sound card, and a DVD Drive.

Thanks guys.
October 18, 2011 11:38:56 PM

Thanks rolli! One thing I was concerned about was that it has 2 12V rails. It was my understanding that one of them @ 25 Amps would be used for CPU and the other rail would be used to power the GPUs. Is that correct? Is there a good spot to see what kind of amps those would be drawing?

Appreciate the help!
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October 18, 2011 11:50:25 PM

One glance here please, the Cooler Master GX, OCZ StealthXtream and ModXtream have creepy reviews when going SLI/CF... for the wattage you're good to go. But i suggest you review your PSU first for the CF/SLI support
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October 19, 2011 12:19:34 AM

Thanks guys. I might be confusing amps. The 12V rails are split, so the modular cables that would be going to my GPU/s would be 12V@25A. 12 x 25 = 300 Watts, so if I was to go over that, I'm assuming I'd crash and cause potential damage.

I'll check out the power supplies you mentioned.
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October 19, 2011 1:04:49 AM

A PSU has a maximum amp for 12V and it has a maximum per rail or set of wiring. Some power supplies are very good about letting you know where that power is setup to flow to and others not so much. Realize that the maximum 12v available to the PSU cannot be exceeded, even if a multiple rail diagram says so. So for instance, a PSU says rail 1 has 25 amps, rail 2 has 25 amps, but the power supply has a maximum 46 amp rating. You CANNOT draw both rails in my example to maximum (well you could, but you would exceed what it was designed to do and may fail or trip (ie turn off)).

A single rail PSU like many PCP&C units have the full amount of the amp rating available down any combination of wiring (in theory). I say in theory because the cabling can also limit that down to less than ideal, but for the most part yes. The benefit is that you dont have to worry so much about where you connect your cables, only that you do. The downside as that this typically means the manufacturer will have to lower or limit its maximum available amps and thus reducing the watt rating.

In general both sides claim to be a better design. In general it is good to have at least 16-18 amps per 12v rail or more (as newer GPU's use up to around that much to operate). Understand that these are maximum ratings and do your research on your particular hardware. There are other factors, as the load on the PSU increases, voltages and power availability can change and hopefully your manufacturer was conservative in their rating. Sometimes not so much.
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