Quick question about p45 boards / Asus Maximus II Formula - PCI-E x16 slots

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prasvt

Gawd
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Dec 8, 2005
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This board isn't an SLI board, but has 2 X16 PCI-E 2.0 slots. I understand that you can do crossfire with ATI cards and in which case both slots run at x8/x8.

If you have two nVidia cards (gtx260 core216, 8800GTS) that obviously aren't SLI'd, as the 8800GTS is only being used for physx, will the 2 PCI-E 2.0 slots remain at x16 each?

I can't tell, though it seems that for physx enabled games / demos, having the 8800GTS handle physx seems to add 6-8fps (cryostasis demo 1080p, 2048x1152), which is nice.

But when I get my GTX 295, it I don't want it being stuck in x8 mode ya know? Anyway I've been googling but I can't find a definitive answer on the x8 / x16 business. Someone on the evga forum suggested they'd stay at x16 each since I'm not doing crossfire or sli..just wanted some corroboration on that. thanks!
 
If you have 2 cards plugged in, it will go to x8/x8 period. It has nothing to do with SLI or crossfire.. it has to do with the number of lanes that the northbridge of the chipset supports.

On that board when you get the GTX 295, you can either have the 295's 2 boards hooked up to the 1 x8 (likely starving the card of bandwidth for it's 2 gpus) with the GTX 260 for PhysX in the other slot also at x8, or you can just leave the 260 out altogether so that you get full bandwidth to the GTX295.

If you go for the second option and leave the 260 out, then it's up to you if you run in SLI or use the second 295 dedicated to PhysX.
 
Well the 295 is replacing the 260, so the 8800GTS would be doing physx. From what I've read, most single cards aren't limited by the x8 lane. But you're right, the 295 would be starved - thanks for the info. I just couldn't find any clear info on this x16 -> x8 business. Once I get the 295, I'll just run it on its own.
 
2 cards = 8x/8x electronically. As BlueStorm said, its a NB limitation. Doesnt matter what the drivers tell it to do. Its a hardware limitation so wether its Crossfire or nV physx...gonna be 8x/8x. Youd be better off doing a GTX285 + 8800GTS physx if you want hardware physx, or just 1 GTX295.
 
Fair enough - actually, I didn't even realize that this board could do crossfire ..had I known I may have tried a pair of ati cards..ah well. But yah thanks for the info. I'll prob take the card out anyway, as I just picked up Fallout 3 which uses havok. And honestly I can run Far Cry 2 at 2048x1152 w/ fps 40-60.

Anyway thanks for the info guys.
 
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