Question Are PCIe 4x16 available for graphic card if 2 x M.2 installed on the motherboard?

[Star2222]

Hi,
on my MSI MAG B550 TOMAHAWK Motherboard I already installed two M.2 SSD on the motherboard itself. But looking at the PCIe table in the manual (screenshot below) it is not clear - to me - if the PCIe E1 still has full PCI 4 x 16 lanes available?

Also why does PCI_E1 shows 3.0/4.0? What decides if it works as PCIe 3.0 or PCIe 4.0?

Sorry if these are stupid questions

And thank you for all help as always!

 

[Imperat0r]

Hello
As you can notice in the table you presented, if you are using both M2 slots, then you will have only 1 PCIe 4.0x16 available.
And that will be PCI_E1.
The only other PCI available will be PCI_E4 which is only 3.0x1
AND one more important thing : M2_2 will only support PCIe x2.

 

[Star2222]

Thank you @Imperat0r

What is the difference between PCIe x2 and x4, are they the PCIs lanes?

If so, does it then mean that my second M.2 drive (a WD_BLACK SN750 1TB High-Performance NVMe M.2NVMe) is actually running at half of its speed?

Thank you

 

[Imperat0r]

The difference between x2 and x4 is the speed you have for your PCIe because in 2x you use 2 lanes and in 4x you use 4 lanes.
As the motherboard manufacturer said, yes, when you use both M2 SSD's, the one inserted in M2_2 will work only in PCIe x2 mode.
In term of speed that won't be a disaster. M2 NVME already have a good speed compared to M2 SATA.

A single PCI-E 3.0 lane has a theoretical throughput of 8 GT/s (gigatransactions per second), which equals 985 MB/s. The x2 marking implies two lines, that is, speeds up to 1970 MB/s.

I believe you will be ok.