Okay, so Pcie lanes?

Aladdad

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i need a quick simple explanation, just so i can have better knowledge :) so when a CPU like the 6700k show max of Pcie lanes is 16 and a motherboard has 2 pcie slots that are x16 does that mean running 2 gpus will run at 16x16 or 8x8?

if it runs at 8x8 then wouldn't that cause bottlenecking? wouldn't it be bad to run Sli on a 6700k then?
assuming the motherboard can handle up to 3 cards with an 6700k will that mean it will run the cards in 8x4x4?

i was looking at some benchmarks of 980 Ti in Sli on 16x16 and 8x8 and there were some huge difference in performance.
 
Solution



most modern motherboards will have a separate x1/x4 slot for soundcards and such


however you need to make sure they dont share bandwith with the main pcie slots as some motherboards do


good motherboards force the x1/x4 slot bandwith sharing with a SATA plug for example, and not the main pcie slots


when that x1/x4 slot is used, the SATA plug with shared bandwith will become non functional

maxalge

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depends on motherboard, but yes most good ones will do x8, x8

going from x16 to x8 is a loss of 1 - 2% percent


x8, x8 is perfectly fine for any two cards in SLI or CF

you dont want to go x4 though
 

Aladdad

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So, Say im using a i6 6700k and running an Sli config, that will run my cards in 8x8 right? but adding a sound card for example is going to use x1? will will force a card to run at x4? which will leave me with x8 on one card x4 on another and x1 on the sound card?
 

maxalge

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most modern motherboards will have a separate x1/x4 slot for soundcards and such


however you need to make sure they dont share bandwith with the main pcie slots as some motherboards do


good motherboards force the x1/x4 slot bandwith sharing with a SATA plug for example, and not the main pcie slots


when that x1/x4 slot is used, the SATA plug with shared bandwith will become non functional

 
Solution

wildcard1978

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actually if running dual or quad sli the good boards run x16 mode for both cards specially in quad sli quad sli needs the extra bandwith when yopur dealing with 2 cards with dual gpus per card.

and pci express lanes are now totatale by cpu and main board . newer boards have but loads of pci exptress lanes and adding more with each revision the even adding m.2 slots to main board now that use the cpus pci express lanes and not the motherboards . basically ya got to search for those board but the rerouthed the pathways of the m.2 slot on newer board that go straight to the cpu and don't even go to the chipset or piggy bad the pci express bus . hope that helps