I have two XFX HD 7870 I bench marked them with furmark after I was playing a game and my FPS dropped to about 20 from 50-60. my 2nd card works fine and get 1000mhz but the 1st one it says it is getting 450mhz. I've checked my Radeon settings and the clock speeds are still set to stock no overclocking or anything. If anyone has any ideas what may cause the issue thatd be greatly appreciated. Also after a computer restart the card reads at 1000mhz for a few seconds the tempature hits 102 celcius then the core clock sets its self to 450mhz. It seems like its over heating but I'm not sure.
If the card is hitting 102C, then it is naturally throttling down to protect the card from overheating.