The info about lane sharing can be hard to find in the official specs.
I have Asus B650E-E motherboard and the problematic slot is #3 M.2 slot.

As soon as I put an Nvme drive in slot #3 my GPU lanes get cut from 16 to 8 lanes. Even on my 7900XTX that is still on gen4.
But I can use 3 Nvme drives in slot #1, #2, #4 + 4 Sata drives + 10Gbit LAN card + tons of USB and all is fine. It's just this one M.2_3 slot.

Official specs look like this:
https://rog.asus.com/motherboards/rog-strix/rog-strix-b650e-e-gaming-wifi-model/spec/

AI in my case is correct telling me that the exact slot M.2_3 is sharing lanes with the main GPU PCIe slot.

You'll need to provide specific models of the motherboards you're referring to if you want people to look at their manuals and tell you this.

However, yes it is not uncommon that one or more PCIe device slots are shared/switched with another slot/device/controller so populating one will disable the other.

For example, the Asus PRIME Z790-A Wifi has 4x M.2 slots. The first (top) one is M.2_1 which is fed directly from the CPU, the other 3x M.2 slots are fed from the chipset. It also has 2x PCIe x16 (physical) slots and it supports PCIe bifrucation and their "Hyper M.2 x16 card". If you populate just the M.2_1 slot the PCIe x16 slot for your GPU will run at full lanes. If you populate BOTH M.2_1 and M.2_3 on the "Hyper M.2 x16 card" then the PCIe x16 slot for your GPU will run at x8 mode.

The "marketing" pages aren't always going to give you that type of detail / limitations. You'll usually need to download the manual and read it to look at the block diagram of how things are connected and they will list device population limits/designs like this in the manual.

引用自 C1REX：

The info about lane sharing can be hard to find in the official specs.
I have Asus B650E-E motherboard and the problematic slot is #3 M.2 slot.

As soon as I put an Nvme drive in slot #3 my GPU lanes get cut from 16 to 8 lanes. Even on my 7900XTX that is still on gen4.
But I can use 3 Nvme drives in slot #1, #2, #4 + 4 Sata drives + 10Gbit LAN card + tons of USB and all is fine. It's just this one M.2_3 slot.

Official specs look like this:
https://rog.asus.com/motherboards/rog-strix/rog-strix-b650e-e-gaming-wifi-model/spec/

AI in my case is correct telling me that the exact slot M.2_3 is sharing lanes with the main GPU PCIe slot.

your M.2_3 slot is Pcie 5.0, that is why i think

引用自 PopinFRESH：

You'll need to provide specific models of the motherboards you're referring to if you want people to look at their manuals and tell you this.

However, yes it is not uncommon that one or more PCIe device slots are shared/switched with another slot/device/controller so populating one will disable the other.

For example, the Asus PRIME Z790-A Wifi has 4x M.2 slots. The first (top) one is M.2_1 which is fed directly from the CPU, the other 3x M.2 slots are fed from the chipset. It also has 2x PCIe x16 (physical) slots and it supports PCIe bifrucation and their "Hyper M.2 x16 card". If you populate just the M.2_1 slot the PCIe x16 slot for your GPU will run at full lanes. If you populate BOTH M.2_1 and M.2_3 on the "Hyper M.2 x16 card" then the PCIe x16 slot for your GPU will run at x8 mode.

The "marketing" pages aren't always going to give you that type of detail / limitations. You'll usually need to download the manual and read it to look at the block diagram of how things are connected and they will list device population limits/designs like this in the manual.

i did download the manual, as i said, and there is nothing about it.

why dont use the other slots .they should be wired to the chipset and wont steal bandwidth

The answer to your first question is: NO
You can never trust AI answer.

Ask AI again. Then write "I read in Asus documentation that pcie lanes are not shared on my motherboard"
See what it says.

引用自 smallcat：

why dont use the other slots .they should be wired to the chipset and wont steal bandwidth

I know that already, but why not use all of them? you clearly dont get the question mate, what i say if using any m.2 slots could affect the PCIE x16 gen 5 slot, they should have stated it on their specs page and manual, but theere is not, and AI chats says there is lol...

引用自 BurakZG：

The answer to your first question is: NO
You can never trust AI answer.

Ask AI again. Then write "I read in Asus documentation that pcie lanes are not shared on my motherboard"
See what it says.

it says its because of marketing... like asus trying to scam people? no chance they (ASUS) would opt for unnecassary after shop complain from people

引用自 VALORHEART：

引用自 PopinFRESH：

You'll need to provide specific models of the motherboards you're referring to if you want people to look at their manuals and tell you this.

However, yes it is not uncommon that one or more PCIe device slots are shared/switched with another slot/device/controller so populating one will disable the other.

For example, the Asus PRIME Z790-A Wifi has 4x M.2 slots. The first (top) one is M.2_1 which is fed directly from the CPU, the other 3x M.2 slots are fed from the chipset. It also has 2x PCIe x16 (physical) slots and it supports PCIe bifrucation and their "Hyper M.2 x16 card". If you populate just the M.2_1 slot the PCIe x16 slot for your GPU will run at full lanes. If you populate BOTH M.2_1 and M.2_3 on the "Hyper M.2 x16 card" then the PCIe x16 slot for your GPU will run at x8 mode.

The "marketing" pages aren't always going to give you that type of detail / limitations. You'll usually need to download the manual and read it to look at the block diagram of how things are connected and they will list device population limits/designs like this in the manual.

i did download the manual, as i said, and there is nothing about it.

It does, it tells you specifically what I noted above; if you configure PCIe bifrucation in BIOS to use their "Hyper M.2 x16 Card" and you populate more than the first M.2_1 on that card then your GPU slot will be cut down to operate with x8 lanes.

Otherwise if you are doing a normal / typical build, you'd install your primary M.2 SSD in the top M.2_1 slot on the motherboard (just above the top PCIe x16 slot), install your GPU in the top PCIe x16 slot and they will both have their full lanes available. Most likely you aren't going to be using the Hyper M.2 x16 Card so you shouldn't have any issue.

AI isn't going to really be a good resource for something like this, at least yet. It is seeing the notes/references to M.2_1 and M.2_3 ON the Hyper M.2 x16 Card as the same as the M.2_1 and M.2_3 slots on the motherboard and incorrectly conflating them.

no
like every other ai, they just lie and tell you what you want to hear

look up the board specs
the sb does not use pci-e lanes
but the sb can have a few lanes to it

what board are you looking at exactly?
there are several asus z970 plus boards


and pci-e lanes are also dynamically allocated
when the gpu does not need all of its lands/bandwidth, it can allocate some to other devices, cutting it to pci-e x1-x8

if a device is pci-e 5.0 it can work with others that are 4.0
only forcing them lower if the cpu or board are limiting the pci-e rev



on this board
Asus PRIME Z790M-PLUS Micro ATX LGA1700 Motherboard
https://www.asus.com/motherboards-components/motherboards/prime/prime-z790m-plus/
m.2_1 goes to the cpu
while m.2_2 and m.2_3 go to the sb, along with m.2(wifi) which is e key for wifi nic

引用自 _I_：

no
like every other ai, they just lie and tell you what you want to hear

look up the board specs
the sb does not use pci-e lanes
but the sb can have a few lanes to it

what board are you looking at exactly?
there are several asus z970 plus boards


and pci-e lanes are also dynamically allocated
when the gpu does not need all of its lands/bandwidth, it can allocate some to other devices, cutting it to pci-e x1-x8

if a device is pci-e 5.0 it can work with others that are 4.0
only forcing them lower if the cpu or board are limiting the pci-e rev



on this board
Asus PRIME Z790M-PLUS Micro ATX LGA1700 Motherboard
https://www.asus.com/motherboards-components/motherboards/prime/prime-z790m-plus/
m.2_1 goes to the cpu
while m.2_2 and m.2_3 go to the sb, along with m.2(wifi) which is e key for wifi nic

here: thesee 2

https://www.asus.com/motherboards-components/motherboards/tuf-gaming/tuf-gaming-z790-plus-wifi/techspec/

https://www.asus.com/motherboards-components/motherboards/prime/prime-z790-a-wifi/techspec/

引用自 VALORHEART：

引用自 _I_：

no
like every other ai, they just lie and tell you what you want to hear

look up the board specs
the sb does not use pci-e lanes
but the sb can have a few lanes to it

what board are you looking at exactly?
there are several asus z970 plus boards


and pci-e lanes are also dynamically allocated
when the gpu does not need all of its lands/bandwidth, it can allocate some to other devices, cutting it to pci-e x1-x8

if a device is pci-e 5.0 it can work with others that are 4.0
only forcing them lower if the cpu or board are limiting the pci-e rev



on this board
Asus PRIME Z790M-PLUS Micro ATX LGA1700 Motherboard
https://www.asus.com/motherboards-components/motherboards/prime/prime-z790m-plus/
m.2_1 goes to the cpu
while m.2_2 and m.2_3 go to the sb, along with m.2(wifi) which is e key for wifi nic

here: thesee 2

https://www.asus.com/motherboards-components/motherboards/tuf-gaming/tuf-gaming-z790-plus-wifi/techspec/

https://www.asus.com/motherboards-components/motherboards/prime/prime-z790-a-wifi/techspec/

Both of those will work fine with an x16 GPU in the top PCIe x16 slot, an M.2 SSD in the top M.2_1 slot, and 3 additional M.2 SSDs in the M.2_2, M.2_3, and M.2_4 slots fed from the chipset. Both of them will cut your GPU lanes down to x8 if you get their Hyper M.2 x16 Card, enable PCIe bifrucation in BIOS for it, and populate more than just the M.2_1 ON that card.

引用自 C1REX：

The info about lane sharing can be hard to find in the official specs.
I have Asus B650E-E motherboard and the problematic slot is #3 M.2 slot.

As soon as I put an Nvme drive in slot #3 my GPU lanes get cut from 16 to 8 lanes. Even on my 7900XTX that is still on gen4.
But I can use 3 Nvme drives in slot #1, #2, #4 + 4 Sata drives + 10Gbit LAN card + tons of USB and all is fine. It's just this one M.2_3 slot.

Official specs look like this:
https://rog.asus.com/motherboards/rog-strix/rog-strix-b650e-e-gaming-wifi-model/spec/

AI in my case is correct telling me that the exact slot M.2_3 is sharing lanes with the main GPU PCIe slot.

i just took a look at your MB manual and in the manual it clearly states that M.2_3 is sharing Lanes with PCIE x16 slot. but noth on the web page. in my case, these z790 manuals both of them not stating lane sharing or lane conflicts, both on the web page and in the manual

引用自 PopinFRESH：

引用自 VALORHEART：

here: thesee 2

https://www.asus.com/motherboards-components/motherboards/tuf-gaming/tuf-gaming-z790-plus-wifi/techspec/

https://www.asus.com/motherboards-components/motherboards/prime/prime-z790-a-wifi/techspec/

Both of those will work fine with an x16 GPU in the top PCIe x16 slot, an M.2 SSD in the top M.2_1 slot, and 3 additional M.2 SSDs in the M.2_2, M.2_3, and M.2_4 slots fed from the chipset. Both of them will cut your GPU lanes down to x8 if you get their Hyper M.2 x16 Card, enable PCIe bifrucation in BIOS for it, and populate more than just the M.2_1 ON that card.

yea it seems AI is just telling the Info regarding Hyper Card lol, not gonna use hyper pcie cards.

i think you ll always have 16 lanes for the GPU on both motherboards