PCIE advice

Techie-V2 · 12 Mar 2022 at 14:34

Hi,

I'm after a bit of advice with PCIE lanes.

I have a Gigabyte x470 aorus ultra with a rtx2060. Current storage is an 2.5 ssd for storage and a 2tb mechanical drive for data.

I have acquired an 250gb nvme m.2 drive that I want to use as my os drive but I'm unsure which slot on the motherboard to plug it in to as I have read about m.2 dives needing x number of pcie lanes and the graphics card also needing x number of lanes.

Can anyone advise as to which slot on the board to use to get max performance.

If it helps the pc is used for all kinds of games plus video editing.

Thanks in advance

Dg834man · 12 Mar 2022 at 15:50

Top m.2 usually has lanes straight to the CPU that aren't shared, same with the top pcie x16 slot, what does the manual for your board say?

Techie-V2 · 12 Mar 2022 at 16:32

That's where I become unstuck. I'm sure I read something when I bought it about it sharing bandwidth but I can't find it now. It says the m2b socket shareds bandwidth with the pcie x4 sockets but I'm sure I've read something elsewhere about the other socket sharing bandwidth as well. I though I would find it a bit strange if the primary m2 socket shard bandwidth with the x16 pcie socket???

Donnie Fisher · 12 Mar 2022 at 17:31

dg834man is right I think.

The top m.2 normally has x4 dedicated lanes the CPU and is not shared with anything. you should get best performance in that slot without impeding performance of the GPU/pcie slots.

There are normally then x16 lanes available to be used for the 1st and 2nd pcie slots. if you only put one card in the 1st slot, then that card will get all 16 lanes. if you put 2 cards in each of the pcie slots, then the cpu will issue x8 lanes to slot 1, and x8 lanes to slot 2.

Now this also applies if you have a APU style Ryzen CPU ( like the 3400G, 5600G, 5700G part which have a built in GPU etc ). Because they have a GPU built into the CPU itself, then the CPU will issue x8 lanes to that internal GPU section, leaving only 8 lanes available to the pcie slots on the board. as a result, you can normally only install something into pcie slot 1, and you'll also be limited to x8 lanes for it.

In your case, it reads like you have a normal Ryzen CPU, and a normal GPU. So in your case, put the nvme into the m.2 slot beside the CPU, and the GPU in slot 1, and you should be realising best performance.

Does that make sense ?

Techie-V2 · 12 Mar 2022 at 18:00

Yeah I have a ryzen 7 2700x. The above makes sense.

So I'll put the nvme in m2a which is at the top, practically under the gpu and leave the gpu where it is.

How would I be able to tell if I have it all right after I have done it, like how would I tell that the gpu is still at x16 and not x8 etc.

Thanks!

Donnie Fisher · 12 Mar 2022 at 19:47

the bios normally is able to tell you what gpu card is in each slot and whether its x8 or x16
if the nvme works, its fine ... it shouldn't affect the gpu in anyway.

Tetras · 13 Mar 2022 at 00:41

Techie-V2 said:
That's where I become unstuck. I'm sure I read something when I bought it about it sharing bandwidth but I can't find it now. It says the m2b socket shareds bandwidth with the pcie x4 sockets but I'm sure I've read something elsewhere about the other socket sharing bandwidth as well. I though I would find it a bit strange if the primary m2 socket shard bandwidth with the x16 pcie socket???

My read of your manual says that the third PCI-E 16 (full length) slot is unavailable when the second M.2 slot is used.

I don't see any restrictions on the first M.2 slot.

Donnie Fisher · 13 Mar 2022 at 15:35

the 3rd pcie slot and the second m.2 slot share the same lanes ... use one, you normally cant use the other. The lanes are provided by the x470 motherboard chipset and not directly from the CPU like the other slots.