PCIe lanes question
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rgb#000
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PostPosted: Tue, 27th Jan 2015 11:14    Post subject: PCIe lanes question
I have a i5 2500K which has 16 PCIE lanes, and I have 1 GPU which runs at x16, all was well until i decided that i want to install expansion card

so what happens if i install PCIE x1 expansion card. will it consume 1 PCIE lane forcing my GPU to only run at x8 ?

i tried googling but haven't found a clear answer to my question. they all talk about multi GPU setups and this is not relevant to my problem.
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couleur
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PostPosted: Tue, 27th Jan 2015 11:20    Post subject:
The PCIe lanes are given by your mobo. What mobo do you have?


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rgb#000
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PostPosted: Tue, 27th Jan 2015 11:22    Post subject:
my mobo is Asus P8-Z68 PRO Gen3 which obviously has a bunch of PCIE x1 and x16 ports, problem is, 2500K only supports a maximum of 16 PCIE lanes, that's why my question.
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couleur
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PostPosted: Tue, 27th Jan 2015 11:36    Post subject:
AFAIK the PCIe 1x lanes are provided by the chipset and do not affect the 16 lanes provided by the CPU for the GPU.


"Enlightenment is man's emergence from his self-imposed nonage. Nonage is the inability to use one's own understanding without another's guidance. This nonage is self-imposed if its cause lies not in lack of understanding but in indecision and lack of courage to use one's own mind without another's guidance. Dare to know! (Sapere aude.) "Have the courage to use your own understanding," is therefore the motto of the enlightenment."
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Werelds
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PostPosted: Tue, 27th Jan 2015 11:41    Post subject:
No, don't worry Smile

You're right in that your i5 2500K has 16 PCI-e 2.0 lanes. But so does your Z68 chipset - it has 8 of them in addition to the 16 from the CPU.

Check out this diagram from Intel:


The reason behind this is that those lanes on the CPU are primarily meant to be used with GPUs for obvious reasons. Only GPUs require that much bandwidth really, everything else is fine to run over the Chipset<->CPU DMI.

Which slots are connected to your CPU depends on your motherboard, you'll need to check the manual for that. Don't use the slots that are said to be used for SLI/CrossfireX and you'll be fine. Usually that's 3 slots (x8/x4/x4 if all occupied) - so use the other ones.


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Last edited by Werelds on Tue, 27th Jan 2015 11:43; edited 2 times in total
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Breezer_




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Location: Finland
PostPosted: Tue, 27th Jan 2015 11:41    Post subject:
No it wont drop your speed to 8x, even if it would you are not going to see any speed difference compared to 16x
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rgb#000
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PostPosted: Tue, 27th Jan 2015 11:44    Post subject:
oooh it all makes sense now, thanks guys Smile
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