Pcie x8-x16 How big a diff?

[Boneface]

I was wondering how much of a difference running a card at pcie x8 then at pcie 16? Im using the p5nesli and didnt realize that i had the little card turned the wrong way and its been running at x8 the whole time ive had it...DOH!!!!!...so just wondering how much of a diff it is


thanks
Boneface

[BullGod]

I was wondering how much of a difference running a card at pcie x8 then at pcie 16? Im using the p5nesli and didnt realize that i had the little card turned the wrong way and its been running at x8 the whole time ive had it...DOH!!!!!...so just wondering how much of a diff it is


thanks
Boneface

Huh?

[Grings]

i'd say you're in the best position to answer that question yourself really, how about you tell us how much difference there is:)

[pt]

porb not much on a hd3850, but you should test it and tell us :)

[newtekie1]

I was wondering how much of a difference running a card at pcie x8 then at pcie 16? Im using the p5nesli and didnt realize that i had the little card turned the wrong way and its been running at x8 the whole time ive had it...DOH!!!!!...so just wondering how much of a diff it is


thanks
Boneface

Probably only a minor difference. Though when I did that with my P5N-E SLI the thing wouldn't even boot.

[Hawk1]

I don't get how the card is "turned" the wrong way? Doesnt it go in only one way?:confused:

[DanTheBanjoman]

As posted plenty times before. (http://www.tomshardware.com/2007/03/27/pci_express_scaling_analysis/page8.html)

[DanTheBanjoman]

I don't get how the card is "turned" the wrong way? Doesnt it go in only one way?:confused:

SLI card thingy, turn it around for x16 operation or x8+x8. Early SLI boards had that.

[Boneface]

As posted plenty times before. (http://www.tomshardware.com/2007/03/27/pci_express_scaling_analysis/page8.html)


So from that i should assume not much of a differnce lol. Ill try my COD4 in abit and see if theres any noticeable difference. thanks guys

[DanTheBanjoman]

So from that i should assume not much of a differnce lol. Ill try my COD4 in abit and see if theres any noticeable difference. thanks guys

x8 vs x16 indeed isn't that big of a difference. However I'd still rotate that little card, just because you can and won't cost you a thing :)

[Boneface]

LOL oh i did and thanks to gpuz for showing me that i had it wrong lol

[btarunr]

I don't get how the card is "turned" the wrong way? Doesnt it go in only one way?:confused:

The card when turned into the "SLI mode" enables the second PCI-E slot by re-directing 8 lanes from the first slot to the second while the second slot has its own basic power interface. When in the "single card" mode, all 16 lanes are used by the first slot and the second slot is disabled.

However with revisions to the "16 lanes in all for graphics" SLI chipsets such as the NForce 500 SLI, 550 SLI, 570 SLI, 650i SLI the lane negotiations are performed by the northbridge itself. However a particular board from Abit retains this SLI mode selector card design on its NForce 650i SLI offering (maybe because they retained an old PCB design).

[newtekie1]

Btarunr, the board we are talking about here, the P5N-E SLI, is an ASUS board actually. The card is still commonly used on low end SLI motherboards using lower end chipsets that don't have enough PCI-E lanes to go around.

[xfire]

Is it the same for crossfire?

[btarunr]

Btarunr, the board we are talking about here, the P5N-E SLI, is an ASUS board actually. The card is still commonly used on low end SLI motherboards using lower end chipsets that don't have enough PCI-E lanes to go around.

Oh shit....thanks. It just struck me, there is a NForce 650i SLI board, just that it's made by Abit and not DFI:o

Here she is...the Abit Fatal1ty FP-IN9:
http://www.uabit.com/images/products/large_images/fatal1ty-fp-in9-sli_top_500.jpg

That's a current-gen board based on the NF650i.

Company page (http://www.uabit.com/index.php?option=com_content&task=view&id=32&Itemid=48&page=1&model=338)

[btarunr]

Is it the same for crossfire?

Nope...never has been such a board for CF. The "16 lanes for GFX" Crossfire boards didn't have such a thing however, there was an interesting AM2 board made by ASUS based on the AMD Crossfire 480X, the M2A-MVP (http://www.asus.com/products.aspx?l1=3&l2=101&l3=482). This board was special because, suppose you have to use a single video-card, you would have had to use it in the second (blue) PCI-E slot as that one gets the 16 lanes when you insert a "lane-bypass card" in the first (black) PCI-E slot (You couldn't do the other way). With the lane bypass card removed, you could have both the slots with x8, x8 lane configuration.
http://www.asus.com/999/images/products/1519/1519_l.jpg

The "32 lanes for graphics" chipsets from AMD (AMD 580X, 790 FX) had all 32 lanes from the northbridge. In "16+4 lanes for graphics" such as some Intel P965 and Intel P35 boards, the northbridge feeds the primary card with 16 lanes, the second card would get 4 lanes from the southbridge, again if any PCI-E x1 slots are used the second video-card gets only 2 lanes.

[jammy86]

Check TOMSHARDWARE

[xfire]

You got me more confused than before:o
Correct me if I am wrong but
From what I understood and know a chipset supports x no.of lanes from which pci-e x1 use up some of them. Then for sli/crossfire when single card is used it runs at 16x but when 2 cards are used it is divided by 2 to get 8x i.e the 16x lanes are shared.

[btarunr]

No. For the Intel P965 and P35, there's a fixed number 16 of PCI-E lanes to the video-card from the northbridge, the southbridge shares its 4 PCI-E lanes to the second PCI-E x16 slot and the remaining x1 slots. If a second video card is installed and there's no other x1 card, it gets all 4 lanes from the southbridge, else the video card gets 2 lanes even if just one x1 device is installed. In the older Intel 975X chipset, the lanes are split by the northbridge to x8, x8.

[Monkeywoman]

if your card is pulling more than 60Gb/s than u will notice a difference.