Enough lanes for 2 GPU 2 NVME?

[nyankocool]

I am running Ryzen 3950x and X570 Aorus Pro. I have two graphics cards installed X16 and one X8, and a single NVME. I was thinking to install one more NVME in the middle one.
My question is, are my lanes enough for it?

Now that the upper one is blower card and the below one doesn’t precisely sit over the slot, maybe temps would be acceptable for it.

[MrFigs]

It looks fine to me. The motherboard manual makes no mention of lane-sharing between PCI slots, M.2 slots, and SATA.

For reference, this is your board’s manual (section 1.8, internal connectors):

I have a Gigabyte Z390 board which does share lanes, so my M.2 page looks like this instead:

If there were any similar limitations, I would expect to see them in the same place, since they’re from the same manufacturer. A block diagram would be nice to really put this to rest, though.

[nyankocool]

Thanks for the excellent clarification!

[gordonthree]

Enough lanes means what to you?

Your CPU has 24 lanes total, four are dedicated to the chipset but sometimes some voodoo goes on there as well.

Usually the GPU slots auto switch to 8+8 when two slots are used. That leaves 4 lanes remaining for your nvme at full speed. However again, voodoo, sometimes that m.2 slot will auto switch and you can do 2+2 for dual nvme.

Will less bandwidth impact daily use? I doubt it, but if you go looking for a bottleneck it will show up in specific benchmarks that measure bandwidth.

[HopnDude]

Ahh, the lifelong battle for PCIe lanes to get the most use of a CPU and the motherboard layout. (excluding HEDT CPU/MoBo solutions)

Currently on AM4 (and a boat load of non HEDT Intel boards), if you MoBo has 3x x16 slots;
-Top pinned x16
-Mid pinned x8
-Bottom pinned x4 (using 4 PCIe lanes via PCIe 2.0 speeds over chipset - unless X570 then PCIe 3.0 speeds)

Known issues;
-if you use the bottom M.2 slot (except X570) in a AM4 board, it will disable the bottom PCIe slot
-if you use two GPU’s, most games will only use 1; moreover, the top one when used in crossfire/sli, will get cut to x8 PCIe 3.0 throughput and the bottom will get the other x8 PCIe 3.0 lanes

It may change for Intel platform with new Z490 boards coming out with PCIe 4.0, but at least for AM4 platform on X570 you can use two NVMe’s (one x4 directly to CPU and one via chipset) in RAID 0, if this is what you’re goal is, and the X570 chipset has enough PCIe lane allocation to make full utilization of PCIe 3.0 NVMe drives, possibly even PCIe 4.0 NVMe drives (I haven’t seen many test done).

[w.meri]

The X570 chipset itself actually has a lot of extra lanes, 16 extra lanes to be exact.

Your GPUs will probably split x8/x8 direct to CPU, one NVMe drive will be x4 direct to CPU, and the other NVMe drive through the X570 chipset.

Now the interface between the CPU and the chipset is only a x4 connection, so your second NVMe drive will share the same connection with most of your other general IO. Whether or not that will be noticeable is up to what you do with the second NVMe deive, but for most people I’d say the performance impact would probably be negligible.

[derpuma]

Hi there, I have a little problem with the X570 Aorus Pro and my UNRAID setup.
Today I put a 2nd NVME on into the second M.2 slot of my Board.
In slot 1 I have the same NVME.
PCIe Slot 1 and 2 has two GPUs, one 5700 X and one RX480, the last x4 PCIe Slot has a 10 Gbe Ethernetcard.

In Bios, both NVMEs show up, but in UNRAID when array is stopped, it shows me only the one in the 1st slot…

What am I missing? Help would be great.