How much better is the gtx280 over my gts640?

Was curious, I have what is almost now a old school 8800 GTS640 mb card and works great on all my games at 1920 x 1200. But Im about to upgrade the cpu and mb and was thinking about the gtx280 since the prices have come down now. Anyone upgraded to one of these from a year or so older card as mine. What improvement did you see. I dont want to pay $560 for a 4870 x2 right now and not impressed with only 1gb of the memory being used instead of the 2gb.

It would be over twice as potent as your GTX 640, but for the price, I really wouldn't recommend it all that much. Excepting a few cases where you might want the 9800GX2, there is little reason to get any card more expensive than the GeForce 8800GT that is not part of the Radeon 4800 series; a SLi motherboard is really the only reason.

What do you mean by that? I presume you're talking about the memory quantity of the 4870X2... I think you misunderstand. It has 2GB, but it's split into two pools of 1GB, each dedicated to a single GPU.

But because neither GPU can access the memory that the other GPU has, each pool has to have an EXACT copy of all the data that is in the other one. In effect, the card functions like one with only 1GB of memory, because it can only store 1GB worth of textures, because it has to store everything in DUPLICATE.

Ok I understand that now, I breezed over the description of it before. Thanks for clarifying that for me. Still not worth $560 to me, maybe in a few months it will dip down to what current gtx280 prices are at now.

It's 2 cores in one card, compared to one. Of course it'll perform better. Not a fair comparasion. A single g92 core has certainly been passed over by the gtx200.