4870 has intermittent lagging

[Krossfyre]

I have an XFX 4870 1GB that doesn't really have a "stable" framerate. By that, I understand that some parts of games will be more demanding than others, but I can hear my fan speed up and slow down, almost like the card is changing clocks and whenever it does that, my game slows down (for only like a half a second) and then speeds back up to normal speeds.

Here are my system specs:
Phenom II 720 X3 Black Edition @ 3.25GHz
2GB DDR2-800 RAM
730W Power Supply (Combined 12V Amps are 74)
ASRock K10N78M Mobo

Thanks in advance for your help!

 

[Krossfyre]

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[Krossfyre]

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