Pcie 5 M.2 + GPU Bandwidth Usage

Chillybean · 2026-02-22T09:37:25+0000

Hi Guys

Apologies if a bit of a noob question but i am using 14700k with z-790 main board & 5080 fe. I have had conflicting information regarding the usage of the top M.2 slot.

What i have been told by various sources -

1 = If i use the top M.2 slot this ssd will run at pcie5 speeds, however the 16 lanes will drop to 8 for the GPU meaning the 5080 will be running on pcie5 x 8 & not x 16. Due to the high end powerful card this will not affect performance too much at all as pcie 5 x 8 is roughly the same as pci4 x 16. S best of both.

2 = If i use the top M.2 slot this ssd will run at pcie 5 speeds, however the 16 lanes will drop to 8 for the GPU meaning the 5080 will be running on pcie5 x 8 & not x 16. Due to the high end powerful card this WILL affect performance the high-end card requires the bandwidth.

Which one of these is true as i dont see the point in pcie 5 ssd speeds if the expensive powerful gpu is not going to perform. I dont play anything that is too taxing DCS, MSFS, Nuclear Option, BF6 & Arma

Cheers
Chilly

ED209 · 2026-02-22T09:41:50+0000

Which motherboard are you looking at? as this can vary from board to board.

Only reason to get a PCIE 5 NVME drive is if you are moving big files around or doing video editing etc.

If its just for gaming and browsing the web save the extra and just get PCIE 4

Armageus · 2026-02-22T10:01:11+0000

1% difference, even with a 5090.

NVIDIA GeForce RTX 5090 PCI-Express Scaling

The new NVIDIA GeForce RTX 5090 is the first high-end graphics card that makes use of a PCI-Express 5.0 bus interface. Are you in trouble when trying to run it on PCIe 4.0? What about x8, like when an SSD is using up some bandwidth? We've also tested various PCI-Express 3.0, 2.0 and 1.1 configs...

www.techpowerup.com

Tetras · 2026-02-22T14:17:11+0000

Chillybean said:
Which one of these is true as i dont see the point in pcie 5 ssd speeds if the expensive powerful gpu is not going to perform. I dont play anything that is too taxing DCS, MSFS, Nuclear Option, BF6 & Arma

1. is correct, assuming your board has a PCI-E 5.0 M.2 slot. The performance loss is pretty small, though you obviously need a PCI-E 5.0 M.2 drive to take advantage of the speeds.

There are two main factors in how much performance is lost:
1. The VRAM on the cards (and if the settings in the game exceed it).
2. The number of lanes available on the card itself.

Fewer PCIE lanes and less VRAM = more impact from slot bandwidth.

Big cards are usually less impacted, because they have more lanes and more VRAM.

It would help if you give us the board model. They're not all the same.

Chillybean · 2026-02-22T14:33:52+0000

Hi guys, thanks for the quick replies.

The setup is a 14700k
Asus rog strix z790-e gaming wifi
Rtx 5080 founders edition
64gb corsair ddr5 6400mhz cl32

The board has 1 m.2 slot that is at the top closest to the cpu and gpu slot that is pcie5 +4 other pcie4 m.2 slots

mickyflinn · 2026-02-22T15:02:58+0000

What are you doing that a pcie5 m2 will be of benefit ?

If gaming there's no point stick with a pcie4 m2

Chillybean · 2026-02-22T15:22:00+0000

It is primarily for gaming, i will be streaming the games at some point on twitch and a bit of short videos that will require a bit of editing etc but it is really just gaming.

Tetras · 2026-02-22T15:24:32+0000

Chillybean said:
Asus rog strix z790-e gaming wifi

The board has 1 m.2 slot that is at the top closest to the cpu and gpu slot that is pcie5 +4 other pcie4 m.2 slots

Yup, if M.2 slot 1 is occupied you will lose 8 lanes from the graphics, but the drive will run @ PCI-E 5.0 (assuming the drive IS a PCI-E 5.0 drive, which I don't know from what you wrote).

These lanes are hard wired too, so any drive occupying that slot will take 8 lanes, it doesn't matter what speed.

Chillybean said:
It is primarily for gaming, i will be streaming the games at some point on twitch and a bit of short videos that will require a bit of editing etc but it is really just gaming.

If you watch task manager when you're editing it will help you to see if you're SSD bottlenecked, but these drives are generally only noticeably faster when you're reading/writing huge amounts of data to it. That's not something that many workflows will do (or do enough). If you have purchased a PCI-E 5.0 drive, then I'd probably just use it, regardless of the hit to the GPU, since you already paid for it. If you do not have a PCI-E 5.0 drive, then I wouldn't buy one.