Ryzen 5 3600 PCIe lane assignment

[ottojo]

Hi!

I’m looking for help/answers regarding PCIe connectivity of my 3600:

I am currently using a Ryzen 5 3600 in a “X570 Phantom Gaming 4” mainboard from ASRock.
I want to connect both a RTX 2060 (PCIe x16) and a (QLE7340) network card (PCIe x8).
Using the GPU in the first slot and the NIC in the second slot results in the GPU using 16 lanes and the NIC using 4 lanes. Swapping the devices results in the NIC using its maximum 8 lanes, but the GPU uses only 4.

Is it possible for the bottom slot on the mainboard to use 8 PCIe lanes, or is that a limitation of my system? (The CPU i guess, as the physical slot is large enough for 16 lanes?)
Or am i just not finding the correct BIOS settings to use it in x8/x8 mode?

I read that this CPU has 16 lanes available, with the remaining 8 being used for the chipset and NVME storage (i use one NVME SSD).

Thanks!

[Brutkruemel]

It depends on the mainboard implementation how the slots behave, if i am not mistaken.

The CPU has 24 lanes in total.
Usually set up sth like this:
4 for the chipset.
4 dedicated for one m.2
16 devided amongst the PCIeSlots
Sometimes PCIs slots are using the chipset.
This depends on the mainboard implementation, as far as my understanding goes.

If i checked the manual correctly the second x16 slot will always be at x4 maximum. This probably means it uses the chipset lanes. And the top slot will always be at x16.

So, as i see it, with this mainboard you cannot switch to x8/x8.
But i do not think this is an issue.
Four Pcie4.0 lanes have a bandwith of around 8GByte/s, which is higher than a 40Gbit/s NIC needs.
Even PCIe3.0 lanes probably will be enough.
For the GPU to run with x4 i do not think this will be enough, but that i do not know.

So when you put GPU in the top slot, and the NIC in the second long slot i think everything will be fine.
But if you need to run at x8/x8 i think you need a different motherboard. At least as far as i see from the manual.

[mutation666]

@ottojo

Is it possible for the bottom slot on the mainboard to use 8 PCIe lanes

no, check your motherboards manual it will show you all the lane assignments and what happens when do do certain things and whats through the chipset vs direct to cpu.

AMD Ryzen series CPUs (Vermeer, Matisse)

• 1 x PCI Express 4.0 x16 Slot (x16 (PCIE1))*
  AMD X570 Chipset
• 1 x PCI Express 4.0 x16 Slot (x4 (PCIE3))*
• 2 x PCI Express 4.0 x1 Slots

[Lithely]

You should have read up on Boards with PCIe Multiplexers. Where you can run things in 8x/8x mode instead of the 8x/4x mode.

But Mutation666 answered your question. the feature your looking for is a hardware implementation on more expensive boards.