Question New gaming build for 5080 -- want to future proof my PCI lanes

[Adamsan11]

Starting to map out a new build.

The plan is to go X670E or X870E + 9800X3D + RTX 5080. No overclocking (I do not fuss with that). I need WiFi 7 and USB 4.0 so I presume I'll be going X870E (while I recognize I still could get that with X670E).

Where I get lost are the PCI lane specifics. I will initially run this build with my current SATA SSD, so the 5080 should have all the PCI highway it needs. But if I opt for a speedy new M.2 down the road, I get a bit lost on the risk of the GPU having to downshift to an x8/x8 shared situation with the M.2.

So, questions:

1) Is there a future-proofed option for M.2 and the GPU to run ideally together? Does such a mobo exist, or is this simply the PCI lane limit of the AM5 mobos out there? I see some gaming mobos with two 'full' PCI 5.0 x16 slots, but a quick check of those mobo's manuals says 'see bifurcation table, x8/x8 may occur'.

2) Is there some standardized terminology in specs I can look for re: coexistence of PCI 5.0 M.2 and GPU lane usage, or must I dig into every prospective mobo's manual to get a clear read on this?

Thx as always. I really appreciate everyone's experience and insight here.

- A

 

[Lutfij]

1| You will need to mention the make and model of the motherboard since different boards might have their lanes wired different to another like for like chipset motherboard. You should be good to go with an NVMe SSD on the M.2 wired to the CPU and yet retain a GPU on the first PCIe slot that's also wired to the CPU without incurring a penalty.

2| Motherboard manuals will have a table/tally to show which lanes/slots/ports are shared and which ones render the other slot, out.

 

[Adamsan11]

Right, so at least from this Aorus X870E 'Master' motherboard, I am seeing this kind of verbiage:

"1 x PCI Express x16 slot (PCIEX16), integrated in the CPU:
AMD Ryzen™ 9000/7000 Series Processors support PCIe 5.0 x16 mode
* The PCIEX16 slot can only support a graphics card or an NVMe SSD. If only one
graphics card is to be installed, be sure to install it in the PCIEX16 slot.
* The PCIEX16 slot shares bandwidth with the M2B_CPU and M2C_CPU connectors.
The PCIEX16 slot operates at up to x8 mode when a device is installed in the
M2B_CPU or M2C_CPU connector."

So I presume this one would be a no-go, right? I need the absence of a 'sharing warning' to be confident the M.2 won't impact the GPU? That's the search process I should use?

Thx,
A

 

[Adamsan11]

^^^ And I'm seeing this fairly consistently in all X870E manuals I am reading. Is this just the nature/limit of that AM5 / Ryzen 9000 architecture w.r.t. PCI 5.0 connections? Choose optimal GPU settings or have an M.2 and a slightly slower GPU?

Is that the deal here?

- A

 

[Adamsan11]

I just reviewed a few x8 vs. x16 gaming side-by-side with a 4090 + PCIe 4.0 it seems that the GPU doesn't really budge more than a few fps in most comparisons.

Any reason to think the 5080 on PCIe 5.0 in x8 (not overclocked or anything) would fare any differently?

Maybe x8 for the M.2 and the GPU won't be that big of a deal?

- A

 

[Adamsan11]

And then I see a mobo that has folks claiming it does not lane share... but it has a PCIe 5.0 / processor linked M.2 slot.

Asus Nova X870E
https://www.newegg.com/p/N82E168131...4TnxHR-_AtbK0ey-zK-IAAg1iCf5nwPp0k5EhXOnxwtFN

So, one hand, there is no reference at all to an x8/x8 split. I read the manual, but it's not structured as specifically as other manufacturers. Does that lack of reference represent some technological flex -- that they can actually have a NVME 5.0 drive running at max speed *and* a 5080 with x16 to itself -- or did they just not share that x8/x8 fine print reality like other manufacturers do?

(Folks are commenting about this mobo has 'no lane sharing' yet you'd think the manufacturer would claim that as a win in marketing materials to sell more units. So why aren't they?)

- A