When I was first testing with cgminer, it would fluctuate because I had AMD overdrive enabled so I could move the power control slider to +20% like everyone was saying to do. Now I have that disabled and don't need that silly slider anymore. I just ran another test with cgminer and I can set the clock to what I want and it stays there. Are you saying you don't install "catalyst control center"? Hmmm maybe that's the real problem. Just tried installing driver without it and it didn't work.
Yes, I always uncheck the "catalyst control center / amd vision control" every AMD driver installation or update. I configure clocks using Afterburner or Trixx (to lower down mem clock on the 6870s and 7950), the cores and the 5xxxx cards are configured via BFGMiner or CGMiner. As all of the games I play run fine without presets or profiles, CCC is just a waste of space.
Just add this to your cgminer.conf or bfgminer.conf:
"gpu-powertune" : "20",
No need for sliders.
