Question Which M.2 Slot to use?

[fgump]

I purchased an ASRock Nova Z790 along with a Samsung 990 Pro M.2 drive. My GPU is an nVidia RTX3060. The motherboard has a ton of M.2 slots. The first M.2 slot supports PCIe 5.0 drive giving 128 Gb/s throughput and the second supports PCIe 4.0 up to 64Gb/s via the CPU lanes. Looking for a recommendation on which slot to place my 990 Pro M2 drive. Using first slot M2_1 makes my PCIe x16 lane go to x8. I prefer drive performance over video as I do more work than gaming. Not sure if it's better since I believe M2_1 slot works directly with the CPU and not chipset. Also would I be better off with a Samsung 990 Evo Gen5 M.2 drive? I chose the 990 Pro Gen4 for faster read/write and longer warranty. Thank you!

 

[Eximo]

Generally with Z790 boards that PCIe 5.0 slots shares bandwidth with the GPU as you have discovered. But many boards offer a mode to switch it to PCIe 4.0 which will use the chipset instead and let you use the slot without reducing GPU bandwidth.

I don't think you will notice a difference between the drives in practice. You need to be able to move a lot of data around for it to matter. So generally if you have another M.2 drive in there that would be constantly making transfers to, or access to a 10Gbps or greater network with a similar SSD on the other endpoint.

 

[fgump]

Generally with Z790 boards that PCIe 5.0 slots shares bandwidth with the GPU as you have discovered. But many boards offer a mode to switch it to PCIe 4.0 which will use the chipset instead and let you use the slot without reducing GPU bandwidth.

I don't think you will notice a difference between the drives in practice. You need to be able to move a lot of data around for it to matter. So generally if you have another M.2 drive in there that would be constantly making transfers to, or access to a 10Gbps or greater network with a similar SSD on the other endpoint.

Thank you @Eximo What would I look for in the BIOS to switch it to PCIe 4.o to use the Chipset so it doesn't share with the GPU? Also would I be better off with a Samsung 990 Evo Gen5 M.2 drive in that primary slot? I chose the 990 Pro Gen4 for faster read/write and longer warranty.

 

[SkyNetRising]

Looking for a recommendation on which slot to place my 990 Pro M2 drive.

Use M2_2 slot. To prevent graphics card slot going into x8 mode.

Also would I be better off with a Samsung 990 Evo Gen5 M.2 drive? I chose the 990 Pro Gen4 for faster read/write and longer warranty.

990 Pro is better.
990 Evo is dramless.