# PCI-E 16x vs. 8x



## joh06937

i have been looking around and it seems that a graphics card in a 16x pci slot will not perform THAT much better than a graphics card in a 8x pci slot. is that true? if i have let's say 2 hd 5770's in crossfire, one in a 16x slot and one in a 8x slot, will the performance be that much lower than 2 16x slots in cf? anyone benchmarked/tried different slots in cf with any graphics card? any help is greatly appreciated.


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## joh06937

it seems most people say about 2-5% decrease in performance. anyone agree/disagree when using the hd 5770? can anyone quantitatively show this (using bus-width, etc.)? this would only be for bonus points (my curiosity)...


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## ScottALot

Yah, I've heard similar claims about a small decrease in performance. I'm not completely sure, but I'm guessing that GPUs barely utilize 8x speeds?


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## StrangleHold

With 5770 your not going to see but a few FPS difference. Now with something like 5850/5870 there would be more of a difference.


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## CardboardSword

I saw a similar article not too log ago. It was doing benchmarks on a 5870 and constricting its bandwidth on a PCI-E 2.0 slot. 16x, 8x, 4x and even 2x. The only SERIOUS hit was on the 2x (Essentially 4x PCI-E 1.0) 4x and 8x were obviously slower, but in some cases, the 8x or even the 4x slot was performing better than the full bandwidth slot. Its obviously not the better way to run a card, but on a powerhouse like the 5870, when the difference is so negligible. This is also only a single card, not CF, so the difference would likely be even smaller in that case. I would be willing to crossfire in a 4x slot even, so long as it is PCI-E 2.0.


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## linkin

I'll have a 5770 running in a PCI-E 1.1 x16 slot soon, i'll let you know how it goes.


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## joh06937

ok thanks linkin93.


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## TomBrooklyn

joh06937 said:


> 2 16x slots in cf?


 I don't think I've seen any motherboards that have two 16x slots, anyway.  

It seems this issue is going to be resurfacing with the advent of the use of SATA3 or USB on P55 mobos.  Is the performance hit still expected to be as modest on this new hardware and implementation?


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## tech savvy

TomBrooklyn said:


> I don't think I've seen any motherboards that have two 16x slots, anyway.
> 
> 
> 
> Theres a few out.
Click to expand...


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## Gabe63

joh06937 said:


> it seems most people say about 2-5% decrease in performance. anyone agree/disagree when using the hd 5770? can anyone quantitatively show this (using bus-width, etc.)? this would only be for bonus points (my curiosity)...



There was a good test posted on OCN comparing the GTX480SLI at 16x and 8x, NO diff. 

Edit, heck. look at this 4x4 test

http://www.hardocp.com/article/2010/08/25/gtx_480_sli_pcie_bandwidth_perf_x16x16_vs_x4x4

16x16 vs 8x8

http://www.hardocp.com/article/2010/08/23/gtx_480_sli_pcie_bandwidth_perf_x16x16_vs_x8x8


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## Gabe63

TomBrooklyn said:


> I don't think I've seen any motherboards that have two 16x slots, anyway.
> 
> It seems this issue is going to be resurfacing with the advent of the use of SATA3 or USB on P55 mobos.  Is the performance hit still expected to be as modest on this new hardware and implementation?



ASUS and EVGA both make them with the NF200 chip. The best 1156 MOBO in my op in the ASUS E-PRO, 8x8 with SATA 3 and USB 3. Price considered. There are better MOBO's for more $  

http://www.microcenter.com/single_product_results.phtml?product_id=0325863


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## linkin

Oh, about my 5770. it ran just fine. got a newer mobo with pci-e 2.0 and a gtx 460 as you probs already know.


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