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Z790 Maximus EXTREME PCIEX 16X_1 LANES at 8X using GEN4 M.2NVME SSD @ M.2_1???

Level 7
Hello Sirs/Madams,

As in the title if I use:
1x GPU in PCIEX 16x_1 (3090TI) and 1x GEN4 M.2 NVME SSD in M.2_1 slot will the PCIEX 16X_1 be reduced to 8x ??

I have been trying to figure this one out for a while and read sooooo many posts, articles etc but I cant find a clear answer.
Hope you can help me out with this one!!

Also a bonus question 🙂 What Z790 Asus board or other brand is out there that can use 5X GEN4 M.2 NVME SSD's on the board itself? (and/or with included DIMM or addon card)

Hope you awesome guys/galls can help me with this one!

Thank you very much!


Level 7
Bump, anyone??

Good day,

the board itself is electrically wired so that as soon as you use a M.2 in the Gen 5 M.2 slot, you'll be limited to x8 for the GPU. In total, you can install up to 6 M.2s without any issues, just keep in mind that only 2 will be directly connected to the CPU except you manage to get your hands on an x8 card which supports 2 M.2s. That way, you can in theory get up to 7 M.2s into the system.

Even though all slots from the PCH are Gen 4, Raiding multiple devices on those slots won't give you much performance benefits as they only have a single connection to the CPU itself.

DIMM M.2: 2 M.2s PCH
PCI x4: 1 M.2 PCH
and one of the mainboard M.2 slots is also connected to the PCH.
That's a total of 4.

CPU itself, you could use the first PCI Gen 5 slot with an add-on card for 2 additional M.2s. In this case, do NOT use the onboard Gen 5 M.2 slot.
Furthermore, there is one more Gen 4 M.2 slot on the board connected to the CPU.

That should give you a total of 7 M.2s. I sadly only tested a total of 6 M.2s myself so far as I got into a few troubles with the custom loop design to actually move the GPU to the second slot in the end.


Just thought I would add:

From what I have researched, running the GPU at x8 is not much of a performance hit.

I have the z690 rog maximus extreme with a 3090ti, and all 5 m.2 slots populated. I have confirmed with technical support that the m.2_1 slot, when populated, causes the pcie_1 slot to drop to x8 link width. And it also disables the pcie_2 x16 slot.

I have decided to leave the GPU at x8 with the m.2_1 slot populated. Hope this helps.