[SOLVED] PCI lanes confusion/clarification

Mar 29, 2019
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can someone give me rundown/clarification about PCI lanes in regards to ports usage, motherboard slots and CPU ability

specifically, when i'm looking at the regular intel cpu, like lga1151 socket, says it has 16pcie lanes
but
a motherboard (still) comes with x1 slots -which seems confusing to me on "gaming oriented" mobos
wouldn't that just take up(/halve) your x16 gpu slot to x8? if used the x1 slots for "stuff" at same time?
or do those specific x1 slots not share lanes with the x16-8-4 "gpu slots"?
(as in could plop gpu in run at x16 or sli at 8x8 -and still pop in a couple of x1 pcie cards for other things "no problem" with no loss?)

and also m.2 "stick ssd" slots, if each takes 4 lanes, are they somehow separate lanes from the "regular" pcie/"gpu side lanes" and (intel specs just not mentioning them)?, or are motherboards coming with m.2 slots that actually reduce gpu bandwidth, making it silly to use 1 or even 2 m2 ssd slots as then it would also just cut your gpu down to x8?

basically i get confused when intel says cpu only has 16pcie lanes, but "there is all this stuff to be used"on xMotherboard; making me think in order to actually be able to use that stuff "fully"/proper one "has" to jump to a diff socked ex. lga2066 to get like 44 lanes or something???

cheers
 
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I am sure someone will write to you a big long list of things, but here is some rundown...

Most Pci-E for GPU is rated at either 8x or 16x (although you will NOT notice the difference between them both)
M2 could just be SATA but when using Nvme it can be UP TO 4x taken.
x1 is fast enough for most add on cards.

It's not the CPU that has just the lanes, but the motherboard you are referring to has them as well.

Maybe this would help you
https://en.wikipedia.org/wiki/LGA_1151
Although, is there any reason you are asking?
99% of us don't even use ALL the lanes we are given already, especially since (as mentioned) 16x is not really used yet in gaming.
 
Reactions: Duncie
The CPU can provide PCIe lanes (mainstream Intel and AMD offer 16) and the chipset can offer PCIe lanes. The motherboard offers various PCIe configurations, but typically a user will only use one of those configurations.

For example, the most common is a GPU and a NVMe SSD. On a modern Intel and AMD platform, the GPU will run at 16 lanes from the CPU and the NMMe will run 4 lanes from the chipset. But if you wanted to run 2 GPUs and a NMVe SSD, then the each GPU would run at 8 lanes. The motherboard just offers different configurations of hardware.

Most users wont need more than 16 lanes for the GPU and 4 lanes for a SSD. If you have a large build for content creation and need a bunch of NVMe SSD, then you may want a CPU that offers more PCIe lanes. So think about what hardware you will use for your system and that will define how many PCIe lanes you need.
 
Reactions: Duncie
Mar 29, 2019
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Although, is there any reason you are asking?
my understanding was that newer gpus began to saturate the pcie3 more to where having it in x16mode could provide performance increase over "if" having xx slots occupied that took the other x4/x8 lanes until pcie4-5 standard gets onboard
not that it's a big issue was just sorta thinking ahead when still on pcie 3 if might run out of lanes if it was only 16 from cpu for the entire board/all ports if i added more ssd or wifi card. Didn't know "chipset" lanes were separate that way, thought that's the ones that were available where would then just "only use 16 of them cos x cpu"

and thanks
 
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my understanding was that newer gpus began to saturate the pcie3 more to where having it in x16mode could provide performance increase over "if" having xx slots occupied that took the other x4/x8 lanes until pcie4-5 standard gets onboard
not that it's a big issue was just sorta thinking ahead when still on pcie 3 if might run out of lanes if it was only 16 from cpu for the entire board/all ports if i added more ssd or wifi card. Didn't know "chipset" lanes were separate that way, thought that's the ones that were available where would then just "only use 16 of them cos x cpu"

On the very highend GPUs (2080ti), I would recommend rolling with 16 PCIe lanes as there will be some performance loss. I would also recommend that because it is a $1k plus GPU and you should have a decent platform to pair with it.

But unless you want multi GPU configurations (which I dont recommend) or you want to run a bunch of NVMe SSD in RAID, then this really wont be an issue for you.
 
Reactions: Duncie
Mar 29, 2019
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But unless you want multi GPU configurations (which I dont recommend) or you want to run a bunch of NVMe SSD in RAID, then this really wont be an issue for you.
thanks
main reason i was asking was i was looking at couple of upgrades
but wanted to make sure that popping in a wifi card and nvme ssd now wouldn't then potentially "waste" /lower a future gpu upgrade too, by eating all its lanes possibly chomping it down to x8(or worse lower).
Since i thought it was determined by cpu and "16 only"/shared across all, and not that there was others/excess beyond that, but nice to know "chipset lanes" are completely their own apparently
 
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