PCI E Lanes and Multiple M.2s

[night sigil]

Hello I hope this is the correct space for this. I just watched the techquickies video "Is SATA Obsolete" and it mentioned PCI lanes and having multiple M.2 s would take up some of your lanes that are also used by the GPU and that I would need to allocate them somehow. With that said if I'm running a GPU (3080ti) and I want to add two M.2 drives (one gen4 and one gen3 to fill my slots; already ordered 🫤 ). Do I have to do something to "allocate" the lanes?
I thought it was plug and play. I was going to put my windows and main programs on the gen4 and all the rest on my gen3. Any help/tips is greatly appreciated. TIA

[night sigil]

👀 it’s about to get installed tomorrow and I want to ensure I don’t bottleneck my GPU. Any tips is better than none. I definitely know the basics of installing and setup/assigning letter etc (disk manager)
The lanes I need more details on how the system will handle it and if I need to change some settings or will it automatically allocate the lanes accordingly. Also would it be best to just get a second sata ssd instead of the second m.2? Thx

[unkempt flower]

What CPU do you have? Depending on the amount of PCIe lanes that your CPU has, you'll be fine. And mostly, the second m.2 slot is anyway hooked up to the chipset, therefore it won't take away any PCIe lanes

[night sigil]

I have a ryzen 5800x which has 16 lanes for the GPU and 4 for storage. From what I’ve read so far it does sound like the second m.2 will take from the GPU causing the GPU to run in 8 lanes instead of the 16 it would normally have. If I use two m.2. So 8 for the GPU, 4 for first m.2 and 4 for the second m.2.
Also I’m almost sure the second m.2 is connected on my PCIe lanes not the chipset/sata area.
My build has a R7 5800x, 3080ti, on a gigabyte b550. Hopefully that extra bit of details helps to figure out the best course of action to maximize my hardware performance.
Let me know. Should I ditch the second m.2 for a sata connected ssd or is the info I read wrong about those lanes? Thanks again

Oh I forgot to mention it is in. But I don’t know if I’m losing performance. I’ve yet to try to game on it. I’m going to download some games tonight. Test tomorrow. Hopefully there is a setting that I could tell the system to give the GPU the full 16 lanes. Let me know. Thx

[night sigil]

Update Need Subject Matter Expert Help (this would also make a great video topic. As I’m sure many people do this not realizing the hit in performance. Just excited to fill the slots.)
Ok I’m not 💯 % sure but it does feel like loss. I’m not seeing the fps I used to but only off by a lil.
Is there a setting I can change to ensure 16 lanes are allocated to the GPU?

[past topaz]

You cannot reallocate PCIex lanes, the routing is decided by the MB maker

[radiant junco]

and they set it up so that 1 m.2 slot can disable a pcie slot or pair of sata ports when being used

[radiant junco]

the top m.2 slot and pcie x16 slot are affected by the cpu, any other m.2 slots, pcie slots andsata ports are controlled via the chipset

[past topaz]

well, generally yes and on 'basic' CPUs at least

[radiant junco]

pretty much all desktop cpu's

[past topaz]

yup basic ones

[radiant junco]

wouldn't call them basic tbh, ryzen desktop cpu's are a reduced sized version of a threadripper, and even then, the threadripper is just an epyc cpu with certain features disabled

[past topaz]

threadripper pro with their 128 PCIe lanes are much more fun

and i won't even speak of the server ones ^^

Anyway to get back on track

[radiant junco]

i would, just because

[past topaz]

on ryzen you should have like we said 16x lanes with the GPU, 4x for the first SSD and 4x for the chipset

[radiant junco]

still though the m.2 slot does not take away from pcie lanes from a gpu

[past topaz]

the second SSD will be connected to the chipset

so no impact on the lanes to the GPU

If you plug anything on the second PCIex slot however that could do a number on the lanes to the GPU

[radiant junco]

@night sigilwhat mobo do you have?

eh, not really, the second pcie x16 slot is electrically wired up as pcie x2/x4 or as pcie x8

[past topaz]

i miss the good old days of having 6/8 PCI slot on a mobo and not having to care for reducing performances by using them all

[past topaz]

yes, and if it's an x8 internal it will usually steal thoses lanes on the first PCIE slot giving you basically two x8 slots

well at least it is the case on my x370 based card

[radiant junco]

not always, but mostly yes also relates to bifurcating the pcie x16 slot to do that

with some of them

[past topaz]

yeark, on the x670e crosshair extreme the second SSD slot seem to be connected to the cpu, sharing the 16 "graphics" lanes

it PCIe 5.0 however but i am not sure what would hapen to an x16 pcie 4.0 card on the first slot

[radiant junco]

not really worth it to deal with 'x' sku mobo's tbh they don't really ad anything significant over a 'b' sku mobo for amd

[past topaz]

well asus only seem to have X SKUs

oh no my bad

[radiant junco]

nothing really, it'll run at gen 4 speeds, just 2 m.2 slots also will use pcie gen 4 x4 speeds

[radiant junco]

very wrong there

[past topaz]

yeah yeah i found the B650 lineup

[night sigil]

Heya. It’s you. Thx for jumping on my topic. I have the GIGABYTE B550 AORUS ELITE AX V2

[night sigil]

Yup that’s what I’m worried about.

The first/top slot is gen 4 and the second/lower m.2 slot is gen 3.
Just for knowledge sake. What or where would I look to see how my mobo handles these things?

[radiant junco]

firstly this

[past topaz]

run GPU-Z it will give you the configuration

[radiant junco]

it will do that with hwinfo tbh, and you get better monitoring

[past topaz]

but also please note that running a card in PCIE 3.0 vs PCIE 4.0 is almost un-noticeable: https://youtu.be/0DKVVtirNM8?t=491 and it's equivalent to running PCIE 4.0 x16 vs x8

[radiant junco]

yeah, a tangent not worth talking about right now

[past topaz]

well HWiNFO give that

while GPU-Z give

i prefer the later ^^

[radiant junco]

from what i'm seeing in it's manual you have nothing to worry about, as it's set up with the top m.2 slot directly connected to the cpu and bottom slot connected to the chipset, no disabling of any ports or slots on the mobo due to only 4 sata ports being used where most will have 6 sata ports whee the last pair of sata ports gets disabled with a m.2 being used

[radiant junco]

the hwinfo one is more accurate

https://download.gigabyte.com/FileList/Manual/mb_manual_b550-aorus-elite-ax-v2_e.pdf?v=24d24cf9acc76ba2c833adbcf9dfc9c7 manual for your mobo @night sigil

[past topaz]

they are saying exactly the same thing, just GPU-Z is not mixing PCIE speed in gen and BW

anyway

[night sigil]

Ok I’m understanding that and thx for the manual link. From the screenshot and most articles I’ve read it seems to default the conversation/configuration to one of each. Which is why it wasn’t clear and I never had two m.2 but decided on this build why not.
But yea I’ll dig through the manual to understand where it explains bottom m.2 using sata chipset for its lanes. That way I’ll know what to look for going forward.
And either way it’s good news and I don’t have to buy anymore parts. I’m done with pc building for a while.
Thx for the info and the help.

[radiant junco]

uses both pcie and sata from the chipset, not sata only

[night sigil]

Because it uses both. Would there be any improvement in performance to switch that m.2 to a sata drive or is the pcie you speak of the four that are dedicated for the chipset and that’s why no difference?

[past topaz]

no differences

well no, it would give worse performances

[night sigil]

Ok perfect.

[past topaz]

because sata is slower

[night sigil]

Yes 🍻
That was the original thought when ordering these parts. Perfect. Thx

[past topaz]

anyway all this is very "academic", in real day usage you won't see much difference

even between sata and nvme

https://www.youtube.com/watch?v=4DKLA7w9eeA

[night sigil]

Yea especially for what I do. I’ll probably barely notice. But I just wanted to ensure I had the best experience for as long as possible. And less cables flopping around was an extra perk.
And didn’t want to bottle neck myself. That initial techquickies video made me question my build.

Ok thx!

[radiant junco]

there is a difference when it comes to nvme and sata m,2's tbh, less so when it comes to m.2 vs sata 2,5