I am putting 2 GeForce 295s onto my e760, both in the PCIe x16 slots provided. However, I want to know if putting a PCIe x1 sound card into one of the remaining PCIe x8 slots will impact performance of the graphics cards. I would put it in the x1 slot, but there might be clearance issues when I put a 40mm x 10mm fan on the northbridge heatsink. Basically, will the x1 sound card in an x8 slot slow down the bandwidth of the video cards in the x16 slots?

I have read posts that said yes, and posts that said no, if you dont mind, post back what you find, for future referance and to help others. I would like to know the answer for future referance, I am running two 295's but am not using any other cards or slots.

I also read an x1 sound card or NIC will not drop the two main PCIE slots on the E760 from x16 to x8 but thats not how it works in practice.  According to this FAQ: http://www.evga.com/support/faq/afmmain.aspx?faqid=58513

E760 - X58 SLI Classified

PCIe slot 1: 16x (8x if slot 2 is filled*)
PCIe slot 2: 8x
PCIe slot 3: 16x (8x if slot 4 is filled*)
PCIe slot 4: 8x
 
*not affected when running 1x PCIe cards like a sound card or Killer NIC

Using a 1x sound card or NIC in PCIe slot 2 should not drop PCIe slot 1 to 8x, but it does with my HT HD and GTX 280s.  I've tried messing with the PE4 settings in the BIOS to AUTO/On/Off and it makes no difference. 

Is there another setting somewhere that changes this?  Anyone else able to get 16x for PE1 and 1x for PE2 with both populated?  Confirmation or feedback from EVGA would also be welcome here thanks.

Slot 2 use will place 3 at 8x and 1 at 8x also. I made the mistake to put my second l/c 280 in slot and placed both at 8x.

This diagram seems to say that PCI-E x1 slots are connected through the ICH10 southbridge, not the x58 chipset itself.
 
The 36 PCI-E lanes seem to be only for the x16 (or x4 slots, on some boards.)
 
It would have been nice if they built in some sort of auto-sensing switch or BIOS toggle to change an x16 slot over to an x1 slot through the southbridge in order to use additional hardware without sacrificing x16 lanes.  Even if the x1 slot had to be routed through the x58 chipset it would be nice to set it at x1 and not have it hog x8 lanes.

Balthazor

This diagram seems to say that PCI-E x1 slots are connected through the ICH10 southbridge, not the x58 chipset itself.
 
The 36 PCI-E lanes seem to be only for the x16 (or x4 slots, on some boards.)
 
It would have been nice if they built in some sort of auto-sensing switch or BIOS toggle to change an x16 slot over to an x1 slot through the southbridge in order to use additional hardware without sacrificing x16 lanes.  Even if the x1 slot had to be routed through the x58 chipset it would be nice to set it at x1 and not have it hog x8 lanes.

The X58 IOH has 36 lanes, since only 32 lanes are set aside for graphics that would leave 4 additional lanes so there is no need to route through the Southbridge, most of those are used anyway for the 2 NIC's and the additional JMicron SATA Controllers.

those boards that use the additional 4 lanes on a PCI-E slot do not allow dynamic bandwidth (they dont change depending on which slots are used they usually stick at 16/16/4) and thats probably why.

It was my understanding that the 1X card would not affect performance, if it was in the 1X slot, but that any card in the 8x slots would, regardless of it's size.

Balthazor

This diagram seems to say that PCI-E x1 slots are connected through the ICH10 southbridge, not the x58 chipset itself.
 
The 36 PCI-E lanes seem to be only for the x16 (or x4 slots, on some boards.)
 
It would have been nice if they built in some sort of auto-sensing switch or BIOS toggle to change an x16 slot over to an x1 slot through the southbridge in order to use additional hardware without sacrificing x16 lanes.  Even if the x1 slot had to be routed through the x58 chipset it would be nice to set it at x1 and not have it hog x8 lanes.

Those ICH10R PCIe lanes can be used to route additional PCIe slots, but in many cases they are already used up by various onboard peripheral devices like additional SATA/IDE controllers, NIC, onboard sound.  Also, I coulda swore ICH10R was only PCIe 1.1 and 250MB/s and not 500MB/s which is why they need a PCIe bridge for proper SATA 6Gb/s and USB 3.0 support with 3rd party controllers.  Anyways, not that important. 
 
But ya, most X58 stick to using the 36 PCIe lanes to the X58 chip for the expansion slots I believe.  The P55 does route the additional x4 lanes through the P55 PCH though.  I suppose hoping EVGA had built in some kind of lane redundancy and switching so that x1 didn't drop bandwidth would've been wishful thinking, but the FAQ gave me hope coupled with the fact EVGA was one of the few boardmakers with the foresight to split their two main x16 slots with an additional slot worth of spacing.
 

Moltenlava
Guess Chizow and anyone else experiencing this needs to contact EVGA since it should be working like EVGA states it should work.

Ya its not working properly which is why I was hoping more people had experience with this and could provide feedback.  I posted a link to this thread in the EVGA BIOS thread so hopefully Shamino or Jacob can take a look into it.  I'll probably put in a support ticket as well and try to figure out if its something that can be fixed via BIOS update or if the FAQ is erroneous.
 
Also, for those who may not think its that important, I'd disagree, I've noticed decreased performance with x8/x8 performance to the point I actually get better performance with a single card @ x16.  The difference doesn't necessarily show up in benchmarks especially because the SLI highs obscure them in AVG, but there's a significant drop in minimum FPS to the point its very noticeable.  For example in MW2, with x16/x16 my FPS with Vsync on and 1920 4xAA never drop below 60FPS.  When running at x8, I notice drops in the 40s-50s quite often and its extremely noticeable and detrimental to gameplay and in-game performance.

Ok, so that's another thread dealing with the same problem that I _will_ have (don't have completed my build yet). Please see this thread, too, for reference: http://forums.evga.com/tm.aspx?m=82661

At the moment my (personal, sorry for getting slightly offtopic) concern isn't the use of x1-cards in the x16/x8-slots, but that using an x8-(RAID)-card in any one of the four x16/x8-slots is allegedly (according to chizow and hagatha) limiting bandwith of both x16-slots to x8!
If that's true, it's ridiculous, as it's simply not necessary. 3 cards in 4 slots can have a total of 32 lanes, but the board will only give them 24??? It's also contradictory to what their FAQ (and common sense) says.
It's logical that using an x8-card will drop one x16-slot to x8, but not both!

Can anybody confirm this behavior?