Yes and no. You see that there are multiple factors like performance scaling, the drivers involved [stability] et al that gets into the play once you mention
SLi OR
CrossFireX.
Also the answer to the next question is also no, two cards from different companies cannot be put into SLi OR CrossFireX. You need to have two graphics cards from the same company, same family [
so essentially same company and same power] to implement SLi / CrossFireX.
Also I doubt the nVidia 8400GS will support SLi. What is the rest of your system configuration [this also plays a BIG part]?
I noticed you have mentioned your motherboard and again it does not support a multi-GPU setup, so this solution is out of the equation for you.
Hope this clears your doubts, Cheerio!!
AMD motherboards lacked SLi support after it bought over ATi [c. 2006], till the advent of the AM3+ platform this year. Also OP cannot SLi two 8400GS [they do not have SLi headers on them].
There are a lot of modalities to this Shakti --
- whether the motherboard / chipset is supportive of SLi / CrossFireX since inception OR uses a seperate controller chip to achieve this.
- whether the PCIe slots are x16 / x8 OR x4 [after x8 it is pointless to CrossFireX OR SLi cards due to the lack of bandwidth over the bus].
- Generally most budget Intel offerings only offer CrossFireX support only higher end models supported SLi. AMD motherboards [excluding current generation 9** series] were locked out by nVidia because AMD had acquired their rival ATi in 2006.
I am generalizing all this information a lot, so please google all this and get a more holistic view of the technology.
Hope this helps, Cheerio!!