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Author Topic: Powering a GPU from 4-pin Molex  (Read 8321 times)
maxpower
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May 15, 2013, 12:58:53 AM
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I bought a Sapphire 7850 card recently, and it came with a cable with 4-pin Molex on one end, and a normal 6-pin PCIe connector on the other. It looks like the intent is for the user to connect it to a power connector that would normally be used with a DVD drive. Since I had a free PCIe connector, I scrounged a PCIe cable and used that instead.

Looking to the future, though, I have two cards that use a single PCIe connector each, and two PCIe connectors available from the power supply. Sometime soon, I'd like to upgrade one of those cards to a more modern card that requires two PCIe connections. If I did that, is it realistic to think I could power the 7850 from a 4-pin Molex? My power supply has the wattage (it's 980 watts, I'm pulling 550 now), but I've never seen a Molex to PCIe cable before.

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notaek
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May 15, 2013, 03:44:25 AM
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Yeah I use em with no problem.  They're nice because some PSUs have a lot of wattage but they lack on the PCIe connector side of things.  If you use some of the adapters you can fit a few more cards in. 

Make sure that you are using the connectors with 2x4pin molex on em



rather than one with just 1x4pin molex



They might work but a few guys posted a couple weeks ago with their cables burning out because the one molex to pcie couldn't supply enough power.

maxpower
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May 15, 2013, 11:44:30 AM
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Thanks, notaek. Strange that the 7850 only came with a single Molex to PCIe adapter, rather than a double Molex like the one you posted.

Relatedly, has anyone had success powering a card from spare SATA power, using a cable like this one? http://amzn.com/B007Y91B80

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rick2718
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May 15, 2013, 11:51:29 AM
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I run a 7850 from a 250w supply using the 4pin dvd, and a second 7850 from a 305w supply also using 4pin - pcie.
They have been running continuously for a couple of months with no cable-overheat issues... no issues
of any kind really. 365kh each

The 250 supply is right on the edge.

maxpower
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May 15, 2013, 12:56:59 PM
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Thanks, good to have another data point!

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Dyaheon
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May 15, 2013, 02:56:08 PM
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Been using both types just fine with my 5850s. Double is safer though, and single could be bad for power hungry cards.
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