HD 5850 weird performance in source games

[scubba85]

So, I have a bit of a problem. While playing source engine games such as Half life 2, frame rates will sometimes dip down into the 30-40s area. Normally they run around 120-200 or more, but I know that doesnt really matter i just want it to stay at 60 or higher. When I alt tab out of the game and look at gpuz it shows that the gpu usage is only around 40%. Is there a certain reason that it dips this low, and that my video card isnt being used to its full potential? In other games and benchmarks it runs at 90-100% and preforms quite well.

System specs.

Q9550 @ 3.9ghz 18hour prime95 stable
HD 5850
4gb corsair ram ddr2
gigabyte p45mobo
600W ocz psu
1tb samsung f3
antec 300 illusion
asus 22 inch monitor 1680x1050

Using recent drivers, even did a driver sweep to get rid of the old ones before I updated.

Also, temps are good Video card 57c max

cpu 58 max

 

[scubba85]

Ok, so I have tested this over and over, and it is only happening in source engine games, l4d2, half life 2, mods. Any one have any suggestions?

 

[Supa Chiney]

yeah I noticed the same thing while playing Counter Strike: Source, sometimes frames will drop to 60 or so and it doesn't feel smooth, or sometimes frames are at 100 (I have 100 fps max) and the video is kinda laggy like it was at 30 fps. But only happens on CSS:Source, I play Bioshock 2 everything on High without a single issue..

 

[Pailin]

CS:S has been fine for me on my 5850 @ 875 / 4600