Is ddr3 graphics card compatible with intel core 2 duo processor

The RAM on a graphic card work independently from the system RAM. You'll have no problems with a graphic card which has DDR3 or DDR5 VRAM.

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Your CPU doesn't care what your GPU has in Vram. Good luck.

Even I was told that I couldn't run a DDR3 GPU(9800GT) on my Motherboard .Today,I am running a GDDR5 HD 6850 with my core 2 Duo without any problems other than my PSU.   Hope this helps.  

thanx evrybdy    

Your welcome and good luck.