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Old November 19, 2011, 10:49 AM
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Default PCI-E lanes impact on performance

How much to PCI-E lanes affect performance on GPUs? I remember seeing something about this somewhere before but I don't remember where.

I'd like to see an experiment showing how PCI-E lane speeds affect video card performance.

I was thinking a benchmark on each lane (x1 x4 x8 x16)
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Old November 19, 2011, 10:52 AM
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it doesn't, down to 4x (5% negative impact)
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Old November 19, 2011, 11:08 AM
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The difference is so minimal,you don't need to waste any time "experimenting". A benchmark probably won't show anything different at all.
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Old November 19, 2011, 12:47 PM
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Depends on the video card. Higher end cards will see a bigger loss in perf when losing lanes. In the Rampage IV Extreme review that will be going live shortly you can see the diff in SLI of Z68 x16/x8 vs. X79 x16/x16.
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Old November 19, 2011, 12:50 PM
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Can't wait to see that Eld, would be a great comparison. Can we at some point in the future hope to see Z68 tri sli vs x79 tri sli?
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Old November 19, 2011, 02:51 PM
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Manufacturers would have to provide a Cougar Point board equipped with an NF200 chip to provide enough lanes for tri-SLI. Nvidia won't let you use the eight PCI-e lanes from the chipset for its graphics cards, so Cougar Point is limited to x16 or x8/x8. AMD does allow the chipset lanes to be used for graphics, however, so Crossfire can go up to x8/x8/x8.

Tom's Hardware did a nice series on PCI-e scaling a little bit back, though they had to work with the X58 against Cougar Point and P55 boards as X79 had not yet arrived. http://www.tomshardware.com/reviews/...fire,2910.html
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Old November 19, 2011, 03:55 PM
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Yea I can do P67 FTW vs RIVE tri-sli when my 3rd card gets back from RMA.
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Originally Posted by Arinoth View Post
Can't wait to see that Eld, would be a great comparison. Can we at some point in the future hope to see Z68 tri sli vs x79 tri sli?
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Old November 19, 2011, 05:16 PM
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Interesting. I had no idea if the bandwidth provided mattered much to the video performance. I have a board that has a x16 slot and a x4 slot and was thinking about CrossFire I didn't know how the x4 slot would impact performance, but if it's only ~ 5% decrease down to x4 as said I don't think I'll need to invest in a new board.
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Old November 19, 2011, 07:23 PM
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Sounds like you've got an 1156 board... That's a bit of a special case since the 4x slot is running off the chipset rather than directly off the CPU, so the performance hit is more than just normal 16x/4x operation.
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Old November 20, 2011, 08:46 PM
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The board I have is an M4A87TD EVO Newegg.com - ASUS M4A87TD EVO AM3 AMD 870 SATA 6Gb/s USB 3.0 ATX AMD Motherboard

If what you say is true I may go ahead and get a motherboard upgrade too. I haven't found many details on the board though and I guess now it's time to RTM
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