Battlefield 2 FPS Jump

Everytime i go into an online sever for battlefield 2 my fps will jump from like 85 to 50 or 50 to 25 etc... my fps keeps on changing while i'm playing and it's making my game very laggy and i can't play it good. It's not my internet i have a very good connection, i have a cpu at 3.53 GHz, and an ATI HIS x1900xt video card, and 2 gig of ocz gold series ddr2, dual channel ram.

what should i do to fix this?

 

ur cpu is great! mabye its your video card. i think ur's is pretty weak. i suggest at least a nvidia geforce 5700fx. and go to settings in battlefield and change the video cards mhz lower

 

dude are you kidding me? you think an x1900xt is weak and a nvidia is better???

that video card cost me $400, and a 5700fx le edition is 89$ with 4 pipelines and 256 memory. mine has 512 memory and 16 piplines. my video cards memory clock is at about 1550 mhz.

are you being scarcastic or something because that was the worst piece of advice i've ever gotton on major geeks.