Question about M.2 SSD

technerd02 · August 30, 2022

Hello! So a bit of a noobie question - I have a M.2 Slot on my A320M. I have a Ryzen 5 2600,16gb ram and a GTX 1660 ASUS TUF OC. I wonder if adding a M.2 SSD will affect GPU lanes since I heard that m.2 ssd can make a gpu pcie slot go from x16 to x8?

mariushm · August 30, 2022

No, it doesn't work like that.

The CPU has a number of pci-e lanes, for that Ryzen 5 2600 it's 24 pci-e lanes.

The processors with integrated graphics like for example 2200G use 8 out of the 16 dedicated for the video card slot, to connect the integrated video card, so only 8 pci-e lanes will go to the video card slot.

Processors like Athlon 200ge or 3000g will have even less pci-e lanes - 200ge has 10 pci-e lanes (4 for video card, 2 for chipset and 4 for m.2 or 4 for chipset and 2 for m.2, not sure, doesn't matter anyway) and 3000g has only 6 pci-e lanes, 4 for the video card and 2 for the chipset. Hence, M.2 connectors would not work.

Those 24 pci-e lanes are split into 16 lanes going to video card pci-e x16 slot, 4 lanes going to the m.2 connector and 4 lanes going to the chipset.

The chipset then acts like a USB hub, but with pci-e lanes. It takes in those 4 pci-e 3.0 lanes and creates a bunch of pci-e 2.0 lanes - from memory I think the A320 chipset creates 4 pci-e 2.0 lanes, while B350 and B450 create 6 pci-e 2.0 lanes and x370 and x470 create 8 pci-e 2.0 lanes.

So those 4 pci-e lanes are split into pci-e x1 and x4 slots and maybe a second M.2 connector with only one or two pci-e lanes.

So your video card will remain at pci-e 3.0 x16 , the M.2 connector will work at pci-e 3.0 x4 if the controller on the SSD also uses 4 pci-e lanes.

Keep in mind that there's M.2 NVME SSDs which use pci-e lanes to communicate with the PC and get high speeds, and there's M.2 AHCI (SATA) SSDs which use SATA so they're slower (up to around 560 MB/s both ways).

Also, note that even if your system would restrict the video card slot to only 8 pci-e lanes (which is not the case), with that video card it wouldn't really make a difference, that video card is not powerful enough for the difference between 8 or 16 pci-e lanes to make a difference.

Eigenvektor · August 30, 2022

The best way to find out is to look at the specs of your motherboard: https://www.asrock.com/mb/AMD/A320M/index.asp#Specification

If PCIe lanes are shared and reduced by certain things being plugged in, it is usually mentioned here.

If you want to check in even more detail, look into the manual: https://www.asrock.com/mb/AMD/A320M/index.asp#Manual

As far as I can see, the M.2 does not limit your GPU sockets lanes. However you can see that the PCIe2 slot may be limited to x8 on certain CPU models.