Question regarding 16x/8x PCI-E

[arseassin]

Hey everyone, I recently purchased a Gigabyte GTX 275 1792mb super oc edition card (http://www.newegg.com/Product/Product.aspx?Item=N82E16814125293 <its a real beast>) and instead of retiring my 8800gt I decided to put it in sli with my card as a physx card, and I have a few questions regarding this.

First and foremost, I'm using an Asus P5N-E SLI mobo, and the mobo says that it has 2 PCI-E x16 slots, but they run at 8x/8x when in SLI mode, so I was wondering, since technically running with my 8800 as a physx card isnt sli, is it still pumping that first slot with the 275 down to 8x, or is it still running at 16x, and if it is at 8x, what kind of performance loss am I going to experience?

Secondly, I never flipped the little chip between the sli slots that says SLI or SINGLE around, and my mobo does pick up that there is an 8800 in the secondary, and nvidia drivers say its working fine, do I actually need to flip it or is it fine as is?

Thanks for any help you guys can give me!

 

[arseassin]

bump

 

[capt_taco]

You know, there was another thread earlier today where a guy was trying to do the same thing with a GTX 260 and a 9600.

Basically, as far as I can tell, if you have a decent nvidia card that already supports PhysX, the main effect of adding a dedicated PhysX card is to generate more heat and use more power without increasing performance at all.

http://forums.nvidia.com/index.php?showtopic=143047&st=0

A number of people on the nvidia forums were testing out similar setups, and in one case there was a small gain, but in others it actually slowed things down to involve a second card that was inferior to the main card.

So regardless of the bandwidth issue (and yes, I think it will reduce to 8x/8x even if it's not SLI, because the two slots are probably sharing the same lanes) I don't think this is a recommended idea. Dedicated PhysX cards are probably only a good idea if the main one is ATI.