X870E Hero and PCIE lanes/M.2 drives

[TheSoupladel]

I tried posting this on Asus Forum and haven't had an answer.

I currently have an Asus X870E Hero, a 9950x3d, a 4090 GPU and 3x M.2 Drives (Gen5, Gen4 and a Gen3) they are plugged into M.2_1, M.2_4 and M.2_5 and am getting x16 on the 4090 in GPU-Z.

The question I have is if I swap out the 4090 for a 5090, based on my current config above, will I continue to get gen5x16 or will my GPU Get knocked down to x8? I have a 1000w Corsair PSU and technically according to ************ my entire build will fit under the 1000w limit put only just.

 

[spooks]

Yes, you will continue to get PCI-E Gen5 x16. Your CPU has 20 lanes.

PCI-E Lane where you GPU is connected = 16 CPU lanes
M2_1 = 4 CPU lanes
M.2_2/3/4/5 = chipset lanes

 

[TheSoupladel]

Yes, you will continue to get PCI-E Gen5 x16. Your CPU has 20 lanes.

PCI-E Lane where you GPU is connected = 16 CPU lanes
M2_1 = 4 CPU lanes
M.2_2/3/4/5 = chipset lanes

I read something about this which suggests if you put anything in M.2_2 and M.2_3 it causes bifurcation and potentially cuts down the total number of lanes, more so if you put anything in the second PCIEx16 slot so wasn't sure if a gen 5 GPU would impact on anything

 

[pastymuncher]

According to your manual on page 9 it states :-

When M.2_2 and M.2_3 are enabled simultaneously, PCIEX16_2 will be disabled.

Anything else looks ok. It gets worse if you have a 8000 series cpu but you don't have to worry about that.

What a state things have gotten to, £530 for a motherboard and you only get a pair of pci-e slots, one of which will be disabled if you use a certain combination of M2 ports. Even worse is that if you put anything at all in that second pci-e slot then the top one only runs at 8x. Pay more, get less!!

 

[Smffy]

Pasty is correct, just done the same setup on Stix 870E. Read carefully and make sure the M2 is not in the slots which would cause GPU x8.

I don’t know if it’s totally correct but system drive potentially on the one connected direct to CPU and others on chipset lanes. Follow the manual…

 

[Tetras]

The question I have is if I swap out the 4090 for a 5090, based on my current config above, will I continue to get gen5x16 or will my GPU Get knocked down to x8?

General rule of thumb: PCIE lanes are hard wired, regardless of the PCI-E gen. So, if you have 16 lanes now and you change nothing except the graphics card, then you will have 16 lanes after.

Anyhow, you already did the right thing to avoid lane sharing, by using slots 1, 4 and 5.