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Installed 2 5870s.

Left off the left side panel of my case(cooler master haf x), started my computer, installed the drivers and set up the crossfire... yada yada yada... everything worked fine.

Then turned off computer, put left side panel back on, turned on computer, and heard a very loud buzzing (asssuming it was a gpu fan). Checked status of cards (in Windows 7) and the secondary card did not appear.

Turned off the computer, took off left side panel, jiggled power connectors into secondary card, then turned the computer back on, and it worked again. Put the panel on, turned on computer, worked.

Sometime later, turned on computer, and there's that loud fan sound again. What gives?

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I use just about the same setup. During bootup, the fans on my GPUs run really high but after OS post, they go down into auto.

If you still hear the loud noise when your in the OS during idle, you should download HWMonitor to see what temps your GPU cores are at.

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Thanks for link to monitoring software, but doesn't catalyst control center already have all these features? When the problem occurs (again, it's intermittent) the secondary card never appears in my list of hardware (using device manager or catalyst control center) – Merritt Jul 25 '10 at 18:51

The most likely cause is either a cable is hitting the fan or even simpler - the cards are producing a lot of heat and you have insufficient cooling which requires the fan to go at maximum speed.

If it is only one card, and they are identical, you may want to try switching them around - if it is the same one that makes the noise, you could have a defective card.

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Why a downvote? – William Hilsum Jul 19 '10 at 18:57
You got me... I was also going to propose "cable hitting fan". That's what's always caused "very loud buzzing" for me. – coneslayer Jul 23 '10 at 19:23
There were no cables hitting the fan.... problem is noticed immediately at boot up (while cards are cool) so how would heat be an issue? Response to defective card: doesn't matter which card I put in first; switched them around several times. Sometimes happens when I mess with the USB ports in the back (plugging in/out devices) – Merritt Jul 25 '10 at 18:49
@Merritt The reason I said about swapping them around was simply because I wanted to know if it was just one of the cards making the noise or both of them? If it is both of them, it could simply be the way they are designed to work, where as, if it is just one and it makes the same noise in either slot - you have a defective card. lastly, if either card makes the noise but just on one socket, then there could be something more seriously wrong. – William Hilsum Jul 25 '10 at 18:55
@Will sorry for down-vote. No, don't think either card is defective. My problem seems to be related to the power supply. – Merritt Jul 26 '10 at 20:54
up vote 0 down vote accepted

It appears to be an issue with my power supply and/or the power cables that came with it. I was able to recreate the same sound I was hearing by connecting a video card but not plugging it into the power supply. I then tried to connect the 6-Pin PCI-Express Connector cables (2 per card), and while the computer was on, I fiddled with the cables, and eventually I heard the sound again.

My power supply is an Ultra 1000 Watt (not sure same exact model, but looks identical)

My current workaround is to use 2 8" PCI Express 6-Pin to Dual 4-Pin Molex Male ATX Power Cables in the place of the 6-Pin PCI-Express Connector cables that came with the power supply for one of the video cards.

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