Corsair CX400 powering a i5 750 + 5870 ok?

Pneumothorax

Golden Member
Nov 4, 2002
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Treid a search but came up empty.
Currently running a 4830 + i5 750 + SSD + 2tb WD green on a Corsair CX400. Considering dropping in a 5870 1gb. Is the corsair have enough cajones to power the rig?
 

MrK6

Diamond Member
Aug 9, 2004
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Easily. You could give both the i5 and the 5870 a healthy overclock and still have plenty of room to spare.
 

Termie

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Aug 17, 2005
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I have a CX400 and an overclocked 5850/860 combo, but not in the same system. Depending on how hard you push your system, I'm not sure I'd be as confident as others here in putting them together. My 860/5850 uses close to 300 watts at load (measured at the wall). The 5870 is more power-hungry than my 5850 at 5870 speeds, and I've got a light overclock on the 860. I'm pretty sure that if you overclocked both a 5870 and 750 heavily, you'd be pushing that Corsair to the limits. Also note that it only has one PCIe connector, so you'll need to use an adapter for one of the 5870's plugs.

MrK6 - what does your system pull at the wall? I bet you're pretty close to 350w.
 

MrK6

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Aug 9, 2004
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I have a CX400 and an overclocked 5850/860 combo, but not in the same system. Depending on how hard you push your system, I'm not sure I'd be as confident as others here in putting them together. My 860/5850 uses close to 300 watts at load (measured at the wall). The 5870 is more power-hungry than my 5850 at 5870 speeds, and I've got a light overclock on the 860. I'm pretty sure that if you overclocked both a 5870 and 750 heavily, you'd be pushing that Corsair to the limits. Also note that it only has one PCIe connector, so you'll need to use an adapter for one of the 5870's plugs.

MrK6 - what does your system pull at the wall? I bet you're pretty close to 350w.
My typical gaming load is 250-270W from the wall. Also, remember what you're reading from the wall (a la Kill-a-Watt) is not what the PSU is actually putting out - you have to reduce the draw by the PSU's efficiency. Typical PSU efficiencies are in the 80-85% range, so even if you're pulling 300W from the wall, your PSU is only putting out ~250W. This is only 62.5% of a 400W unit's rated maximum, which is well within the recommended safety range. Couple in the fact that we're considering a quality unit like the Corsair, which can handle much more than 400W, and you have nothing to be worried about. This is the beauty of running quality hardware with a quality PSU :thumbsup:.
 

Termie

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Aug 17, 2005
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My typical gaming load is 250-270W from the wall. Also, remember what you're reading from the wall (a la Kill-a-Watt) is not what the PSU is actually putting out - you have to reduce the draw by the PSU's efficiency. Typical PSU efficiencies are in the 80-85% range, so even if you're pulling 300W from the wall, your PSU is only putting out ~250W. This is only 62.5% of a 400W unit's rated maximum, which is well within the recommended safety range. Couple in the fact that we're considering a quality unit like the Corsair, which can handle much more than 400W, and you have nothing to be worried about. This is the beauty of running quality hardware with a quality PSU :thumbsup:.

All good points. Sounds like the OP is in the safe zone here.

And my, that's a mighty efficient rig you have there. What voltages are you running on your CPU and GPU? When I upped the voltage on the 5850 to 5870 levels, power consumption quickly went above 300w in Furmark (which is obviously a bit more taxing than gaming). Decided to keep my GPU overclock to stock voltages for that reason.
 

Pneumothorax

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Nov 4, 2002
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One more thing: As the CX400 only has one 1 PCI-E power connector, can I connect the 2 molex/hard drive connectors from the same cable to the molex/pcie adaptor? Or does it have to be 2 different "circuits"?
 

MrK6

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Aug 9, 2004
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All good points. Sounds like the OP is in the safe zone here.

And my, that's a mighty efficient rig you have there. What voltages are you running on your CPU and GPU? When I upped the voltage on the 5850 to 5870 levels, power consumption quickly went above 300w in Furmark (which is obviously a bit more taxing than gaming). Decided to keep my GPU overclock to stock voltages for that reason.
Thanks, that's how I designed it. I like having a very quiet rig that still does what I need. The CPU idles at 0.92V and loads at 1.2V according to CPU-Z (draw from the wall at idle is ~82W). GPU voltage is set to 1.125V for 925MHz, runs 900MHz on stock 1.0875V. The 58xx cards will consume a lot more power once you start cranking the voltage (remember that power consumption increases quadratically with voltage increase). I think my rig draws in the ~350W range in Crysis when the 5850 is @ 1GHz and ~1.3V.
One more thing: As the CX400 only has one 1 PCI-E power connector, can I connect the 2 molex/hard drive connectors from the same cable to the molex/pcie adaptor? Or does it have to be 2 different "circuits"?
It'd be better to have it draw from two different outputs, but that isn't always the case just because you put them on different lines, as it depends on the CPU's wiring/design.
 

Rifter

Lifer
Oct 9, 1999
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its single rail, it make no differnce whatsoever how you connect the additional PCIe connector. Also that 400w corsair is a solid unit, you will have no issues.
 

Sheninat0r

Senior member
Jun 8, 2007
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and what does that have to do with an i5 750 and 5870? a 5870 uses less power than even a single gtx285.

The implication is that his (the OPs, if that isn't clear) system is much lower power, and therefore he has nothing to worry about in using a quality 400W PSU.