I am thinking of getting a motherboard that has a Geforce 9400 igp http://www.newegg.com/Product/Product.aspx?Item=N82E16813128363 and I was wondering, can I sli my XFX 9800gt with the Geforce 9400 igp? If I can, then how much FPS boost would I get? I know that scince I would sli with an IGP, I would get a small performance increase but its better than nothing.

The only type of hybrid sli supported by 9800 is hybrid power. The type where you get a performance boost is geforce boost technology, and it is only supported by geforce 8400 and 8500 cards. What hybrid power does is it uses the integrated gpu for non-gpu intensive tasks, so your system produces less heat and uses less power. Read here for more info.

Thank for the info. At least getting hybridpower is better than nothing.

actually i don't think the 9400 board supports hybrid power. look at this page: http://www.nvidia.com/object/hybrid_sli_desktop.html

only the amd boards seem to support hybrid power

Can I at least use the 9400 igp as a physx processer while using my 9800gt as my main gpu??

A quick google search found quite a few threads about this, most of which seemed to think you could not, but none of them were very conclusive. To find out more, you could try searching something like "integrated 9400 for physx" or something similar.

it will save u sum £££ when your energy bill comes in...