I also have a XFX DD Ghz edition card displaying these problems. I have been going back and forth with the XFX rep for about 2 months now, they are about to suggest and RMA in the coming weeks they have said. I have actually found a work around to stop the card from doing this. It involves MSI AB and a modded set of drivers.
I have a newer version of the XFX 7970 DD Ghz Edition with a locked voltage regulator. So the images of my overclock you will see are the best I could get and remain stable. Different internet reviewers out there got further so I guess I didn't do great in the silicon lottery.
Here are two images I included. One was just sitting on the desktop, the card was freaking out. Working fine but osculating like a bizzach. The other is of during a 3D game, not super intensive but I should only be running 3D stock clocks the whole time. Too boot every-time it switches speeds while I'm in game I notice a quick shudder in the game as well.
Now to my work around.
Go to this site here: http://benchmark3d.com/amd-catalytst-13-2-beta-7-7900-mod
Download the 13.2 Beta 7 Modded Driver *******ULPS OFF******
Install that driver.
Now install MSI AB and set it up for overclocking with option 2 for power saving options off. Quick internet search will get you rolling on how to set that up.
Then in order to stable the clock and them not change you have to do at least a 1 Mhz over clock on your core and memory. I suggest a 5Mhz it's a more incremental number in OCing.
Save the profile.
Apply the profile.
Once you have applied the profile you and adjust it back to stock clocks if you wish they will now stick.
NOTE: These cards get stupid hot running FarCry 3 and Crysis 3 so I created a very heavy fan profile.
NOTE: I suggest you give it the +20 power setting when doing this. There is no reason to shortchange the card power and stress the components.
NOTE: Once you up clock your card you will be running 3D clock voltage until your restart your computer, that means more heat at idle. Also verified that doing this does not void the warranty since it's specified clocks per XFX support.
NOTE: IMPORTANT: I do not know if the card will throttle itself because of heat. Even with my current fan profile playing very high end games with V-Sync off the card can hover at 73 degrees C. Unwilling to test this theory you will see my fan profile reaches 85% at 70 degrees C which is quite loud.
I included a pic showing my results.
In this last pic you'll see I created a down clocked profile for surfing the web and such. It still uses 3D voltages but I reduced the power consumption and clock speeds to remove unneeded heat adders.Edited by SoloSolider - 3/21/13 at 3:19pm