Confused about PCI-E lane splitting

[CurseTheSky]

Hi guys,

I have an ASUS P7P55D Pro (P55) motherboard. As far as I know, it can run one video card at x16 and two at either x16/x4 or x8/x8.

I'm sticking with a single card at the moment, but I want to add a PCI-E x1 sound card. If I add that, will it affect my single card performance (such as somehow dropping lanes down to x8)? What about if I add a second graphics card later for x8/x8?

Thanks.

 

[MagnusTheBrewer]

I wouldn't worry about it. The folks at [H] pretty much proved that performance remained constant even at X4/X4 for both single cards and sli. In other words, you get the same performance from your card on a X4 bus as a X16 bus.

Here's the article.

 

[CurseTheSky]

I wouldn't worry about it. The folks at [H] pretty much proved that performance remained constant even at X4/X4 for both single cards and sli. In other words, you get the same performance from your card on a X4 bus as a X16 bus.

Here's the article.

Very interesting. I read this article previously: http://www.techpowerup.com/reviews/AMD/HD_5870_PCI-Express_Scaling/25.html, so I wasn't terribly concerned, but still wanted to know if it only had 16 or 20 lanes of total bandwidth, or if there were more (like 24, for example). I also wasn't sure exactly how it splits the lanes up.

 

[MagnusTheBrewer]

According to your manual on page 2-23, your single GPU will run on x16 with a pcie soundcard in the x1 slot. If later you install a second GPU, they will run at x8/x8

 

[CurseTheSky]

Hmm, checking the manual. Why didn't I think of that.

Thanks a lot for the info.

 

[Glendor]

Hi guys,

I have an ASUS P7P55D Pro (P55) motherboard. As far as I know, it can run one video card at x16 and two at either x16/x4 or x8/x8.

I'm sticking with a single card at the moment, but I want to add a PCI-E x1 sound card. If I add that, will it affect my single card performance (such as somehow dropping lanes down to x8)? What about if I add a second graphics card later for x8/x8?

Thanks.

I was accidentally running my 2x GTX275 in SLI at 16x & 4x for months. When I noticed the difference, I relocated the cards to the 8x & 8x slots and noticed a very slight improvement in benchmarks. I then switched them to the 16x & 16x slots, and noticed another very slight improvement in benchmarks. It probably wasn't enough difference to be significant overall, but I did notice a diff. One thing I thought was interesting was that the benchmarks were lower when I wasn't using the SLI bridge on the 16/4 and 8/8 configurations, but the bridge didn't make a diff when at 16/16.

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