I dont know what else to do, tried everything already.

My HD 7770 which is made by Gigabyte and is a Ghz edition Rev 2.0, with the latest BIOS, is underclocking on the middle of the games, it happens randomly and on several games like Planetside 2 and Guild Wars 2.

On some point the screen will flicker and the game will stop for a minute then it comes back with the lowest FPS possible because now my card is at 300/150Mhz (GPU/Memory)

I am on the latest Catalyst BETA available for Windows 8 x64

My system config Phenom II X4 965@3.8Ghz - AMD HD 7770 Ghz Edition - Mobo Gigabyte GA-MA78GM-S2H - Antec HCG-520

I have the same issue with my HD7970. No matter what i do, i can not change the core and memory clock speeds on desktop. They automatically get up to speed on games however. 
Anyone can help? 

Disable ULPS > http://forums.guru3d.com/showthread.php?t=342695

Go to registry and disable Ulps:

[HKEY_LOCAL_MACHINE\\SYSTEM\\ControlSet001\\Control \\Class\\{4D36E968-E325-11CE-BFC1-08002BE10318}]

and change "EnableUlps" to 0 under the 0000 and 0001 and 0003 keys.

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