Question PCIe Lanes, CPU vs Chipset ?

[akiraxiaoyu]

THREAD UPDATED

Hi Guys, i plan to build new PC with :

• ASUS Z790-E GAMING WIFI
• i9-14900K
• NVMe 1TB Samsung 990 PRO
• NVMe 500GB Samsung 970 EVO Plus (from my old PC)
• ASUS ROG STRIX 3070 OC (from my old PC), will update to RTX ROG Strix 4080 maybe next year not sure.

If i go to Asus website to check the specs of the MB, it shows like this :

Questions :
This MB clearly says it supports 14th gen Intel on their website (read here) , but on Expansion Slots section CPU lane it says 13th & 12th gen only.
1. Does it mean i can use 14th Gen Intel but MUST NOT put my GPU Card on the PCIEX16(G5) slot? Because if i put my GPU on that slot, it only support 13th and 12th gen intel

2. I read that usually the top PCIe x16 on motherboard is the best slot for GPU Card, then if i want to use i9-14900K and then put my GPU Card on PCIEX16(G4)_1 a.k.a the second slot, will it bottle neck my gpu card? Or should i use 13th gen and put my GPU card on the top PCIe x16 slot a.k.a PCIEX16(G5)?

3. Let say if i use 13th gen intel, then i put my gpu card on the top PCIe x16 slot a.k.a PCIEX16(G5). There is info says "When M.2_1 is occupied with SSD device, PCIEX16(G5); which is the first top slot; will run x8 only" . So does it mean i MUST NOT put the 1TB NVMe 990 PRO on M.2_1 slot a.k.a the top m.2 socket and have to put it on M.2_2 slot?

I'm newbie, so please someone enlighten me.

 

[SkyNetRising]

I read on the tech specs, it says both support 14th, 13th & 12th intel gen processor, but when i scroll down to Expansion Slots, why on ASUS Z790-E GAMING WIFI it says only support Intel 13th & 12th gen processor not including 14th? Also what does processor gen has to do with expansion slot?

ASUS Z790-E GAMING WIFI came out before release of 14th gen Intel cpus.
They haven't updated those descriptions fully.

In Expansion slots section they talk about supported PCIE version.

In supported cpus section they have updated descriptions though.
Intel® Socket LGA1700 for Intel® Core™ 14th & 13th Gen Processors, Intel® Core™ 12th Gen,

 

[SkyNetRising]

1. Does it mean i can use 14th Gen Intel but MUST NOT put my GPU Card on the PCIEX16(G5) slot? Because if i put my GPU on that slot, it only support 13th and 12th gen intel

No.
It was explained to you above. The board supports 14gen cpus - with appropriate BIOS update.
Descriptions have not been updated, since board was released before 14gen cpus were available.

2. I read that usually the top PCIe x16 on motherboard is the best slot for GPU Card, then if i want to use i9-14900K and then put my GPU Card on PCIEX16(G4)_1 a.k.a the second slot, will it bottle neck my gpu card? Or should i use 13th gen and put my GPU card on the top PCIe x16 slot a.k.a PCIEX16(G5)?

2nd and 3rd PCIE x16 slots work in x4 mode. Only top slot is recommended for graphics card.

3. Let say if i use 13th gen intel, then i put my gpu card on the top PCIe x16 slot a.k.a PCIEX16(G5). There is info says "When M.2_1 is occupied with SSD device, PCIEX16(G5); which is the first top slot; will run x8 only" . So does it mean i MUST NOT put the 1TB NVMe 990 PRO on M.2_1 slot a.k.a the top m.2 socket and have to put it on M.2_2 slot?

If you want 1st PCIE x16 slot to run at x16 mode, then don't use M.2_1 slot.

 

[akiraxiaoyu]

No.
It was explained to you above. The board supports 14gen cpus - with appropriate BIOS update.
Descriptions have not been updated, since board was released before 14gen cpus were available.

The reason why i update and ask again, because when i contacted Asus Support few hours ago, they replied to me :
"We inform you that based on the link https://rog.asus.com/motherboards/rog-strix/rog-strix-z790-e-gaming-wifi-model/spec/ normally the ROG STRIX Z790-E GAMING WIFI Motherboard unit supports the use of Processors 14th generation Intel. Information can also be checked on QVL at the link https://rog.asus.com/motherboards/rog-strix/rog-strix-z790-e-gaming-wifi-model/helpdesk_qvl_cpu/. The 14th generation Intel Processor can be used if there are no peripherals installed in the 1 x PCIe 5.0 x16 expansion slot. If there are peripherals connected to the expansion slot, it is recommended to use the 12th or 13th generation version only."

This is different from your answer, that's why it is confusing me. Didn't they mean if i put my GPU Card on the first PCIe x16 slot then it means i can not use 14th gen cpu?

If you want 1st PCIE x16 slot to run at x16 mode, then don't use M.2_1 slot.

Alright, got you. Eventhough this is abit sad, because it means i would not be able to utilize the PCIe 5.0 i guess? 🙁

 

[SkyNetRising]

they replied to me :
The 14th generation Intel Processor can be used if there are no peripherals installed in the 1 x PCIe 5.0 x16 expansion slot. If there are peripherals connected to the expansion slot, it is recommended to use the 12th or 13th generation version only."

That response makes no sense.
If PCIE 5.0 causes problems, you can switch operating mode to PCIE 4.0 or PCIE 3.0 in BIOS.

 

[akiraxiaoyu]

That response makes no sense.
If PCIE 5.0 causes problems, you can switch operating mode to PCIE 4.0 or PCIE 3.0 in BIOS.

I agree with you, the answer is abit confusing.
So does it mean if i switch mode to PCIe 4.0 on BIOS, it means i can use 14th gen + plug my gpu card on the first slot PCIe x16? What if one day i want to utilize the PCIe 5.0 ? 🙁

 

[faalin]

I had the same issue on an asus board with 14th gen cpu a few months ago.

Installed a NVMe drive in the slot just under the CPU and a GPU in the first PCIe slot, nether of them would work. Ended up moving the NVMe to a different slot and the GPU down to the bottom PCIe slot and everything started working.

Once i fully got the computer up and running i decided to do a Bios update, tada the top PCIe slot and M.2 slot started working. Moral of the story, update the BIOS to the latest version and everything will be fine on the board.

 

[akiraxiaoyu]

I had the same issue on an asus board with 14th gen cpu a few months ago.

Installed a NVMe drive in the slot just under the CPU and a GPU in the first PCIe slot, nether of them would work. Ended up moving the NVMe to a different slot and the GPU down to the bottom PCIe slot and everything started working.

Once i fully got the computer up and running i decided to do a Bios update, tada the top PCIe slot and M.2 slot started working. Moral of the story, update the BIOS to the latest version and everything will be fine on the board.

Hi, thanks for the insights! May i know what MB,CPU, GPU,NVMe did you use?

 

[faalin]

Hi, thanks for the insights! May i know what MB,CPU, GPU,NVMe did you use?

intel i7-14700K
Thermalright Peerless Assassin 120 SE
Asus Prime Z790-A WiFi 6E
G.skill Ripjaws S5 2x32GB 6400MT//s Cl32
Samsung 980 Pro 1TB
Nvidia RTX A4500
Corsair RM750e
NZXT H5 Flow

Built 2 of these for our CAD guys at work.

 

[akiraxiaoyu]

intel i7-14700K
Thermalright Peerless Assassin 120 SE
Asus Prime Z790-A WiFi 6E
G.skill Ripjaws S5 2x32GB 6400MT//s Cl32
Samsung 980 Pro 1TB
Nvidia RTX A4500
Corsair RM750e
NZXT H5 Flow

Built 2 of these for our CAD guys at work.

Prime Z790-A WIFI does not share PCIe lane, neither does the M.2_1 socket, so on your case update BIOS will 100% work. For my case, the PCIe x16 and the M.2_1 are share each with CPU, so it is different case. But still thanks for the insights!

 

[faalin]

3. Let say if i use 13th gen intel, then i put my gpu card on the top PCIe x16 slot a.k.a PCIEX16(G5). There is info says "When M.2_1 is occupied with SSD device, PCIEX16(G5); which is the first top slot; will run x8 only" . So does it mean i MUST NOT put the 1TB NVMe 990 PRO on M.2_1 slot a.k.a the top m.2 socket and have to put it on M.2_2 slot?

I'm newbie, so please someone enlighten me.

Regardless of what cpu you install, be it a 12th, 13th, or 14th gen.

top PCIe slot is PCIeX16(G5)
M.2_1 is PCIe 5x4
M.2_2 is PCIe 4x4

If you install your GPU in the top PCIeX16(G5) and your samsung 990 in the M.2_1 slot you will get the following

PCIeX16(G5) will run at PCIe 5.0x8 speed and your 990 will run at PCIe 5.0x4

If you install your GPU in the top PCIeX16(G5) and your samsung 990 in the M.2_2 slot you will get the following

PCIeX16(G5) will run at PCIe 5.0x16 speed and your 990 will run at PCIe 4.0x4


If i was in your place i would take option 2 because you really wont notice a difference in real world applications between PCIe 4 vs 5 on the 990. You will probably notice the difference between x16 vs x8 on your GPU.


Also note from what i stated in my previous post, depending on what bios version that came with your board. If you install a 14th gen cpu it will boot up but the PCIeX16(G5), M.2_1, and M.2_2 are controlled by the cpu and might not work till you update to the latest bios. At least that is what i found out in my case.