Installing SSDs in M.2 slots 'B' and 'C' will cause PCIe x16 to run at x8 speeds - will this be an issue?

[RhysMusique]

Hey all,

 

Speccing a new PC for when the new X3D chips and RTX 50xx are announced.

Reading up on the motherboard documentation I'm looking at, it mentions that installing M.2 drives in the 'B' and 'C' slots (using CPU PCIe lanes) will cause the PCIe x16 slot to run at x8 speeds.

 

Now the motherboard is X870 and I hope to get either a 9950X3D, 9900X3D or 9800X3D depending on what is available, and so PCIe 5.0 is standard.

 

I have 3x M.2 drives currently in my Z490 board (PCIe 3.0 running an RTX 3090 at x16), and would like to keep the same setup.

If I run M.2 drives in 'B' and 'C', will PCIe 5.0 at x8 speeds bottleneck a theoretical RTX 5080 or 5090 when they are released? Should I be looking to avoid running that slot at x8, or should it not make any difference?

 

Thanks,

Rhys

[OddOod]

It would be helpful to know what specific board you are looking at
As for bottlenecking, very unlikely. I have a 3080ti on an 8x PCIe gen 3 slot and it only lost ~1% of performance. 

[RhysMusique]

6 minutes ago, OddOod said:

It would be helpful to know what specific board you are looking at
As for bottlenecking, very unlikely. I have a 3080ti on an 8x PCIe gen 3 slot and it only lost ~1% of performance. 

Sorry about that - its the Gigabyte X870 Aorus Elite WIFI7 I'm looking at

[OddOod]

Yeah, that's interesting, but I will say that PCIe gen 5 is just *wicked* fast. Even gen 4 is insanely fast. Assuming you aren't doing some wild and weird thing with this machine, you will be perfectly fine. If you want to dodge the question outright, you could replace your current M.2 situation with a single larger drive, or grab a riser card and run it off the other 16x slot

[RhysMusique]

1 hour ago, OddOod said:

Yeah, that's interesting, but I will say that PCIe gen 5 is just *wicked* fast. Even gen 4 is insanely fast. Assuming you aren't doing some wild and weird thing with this machine, you will be perfectly fine. If you want to dodge the question outright, you could replace your current M.2 situation with a single larger drive, or grab a riser card and run it off the other 16x slot

Yeah, so in essence, even if I were to run a gen 4 40 series card on an x8 gen5 slot (at gen4 speeds) that's still equivalent to gen3 at x16, which is what I'm on now with my RTX 3090, so not much of a big deal I guess! Thanks!

[OddOod]

Yup!

[Tridefender]

Unless you are doing ai and cramming gigabytes of data into the vram...

[RhysMusique]

1 hour ago, Tridefender said:

Unless you are doing ai and cramming gigabytes of data into the vram...

Nah the most VRAM intensive thing I do is Flight Simulation now. It can be pretty intensive at times, when approaching certain airports where I have higher definition add-on scenery for, but that's normally in one pop and it's all loaded, never a sustained slog of VRAM usage.

[OddOod]

.....VRAM is on the GPU

Oh, wait, is that a comment on DirectStorage?

[RhysMusique]

On 12/10/2024 at 9:25 PM, OddOod said:

.....VRAM is on the GPU

Oh, wait, is that a comment on DirectStorage?

So I admit to not exactly knowing how VRAM works but I believe I read somewhere/somebody told me that MSFS was extremely VRAM hungry because it basically live-stores textures from bing maps, downloaded straight from the network and rendered in one go? Again I'm not that familiar with how VRAM actually works anyway I just know that fast and more is generally good.

[OddOod]

VRAM is to the GPU (actual silicon, not whole card) as RAM is to the CPU. It's where the data actually in flight (pardon the pun) lives. So fully and partially rendered frames as well as meshes, light, and texture data.
But that's entirely different from storage which is just where the data is sourced from, though there is also definitely tech to stream that data over the network.