whats the use of a 2nd PCI-E x16?

[EzioWar]

Hi, i see many mobos have two PCI-E x16 slots, where primary PCI-E x16 is for my gpu, but 2nd one only supports upto X4 or something. I'll never use more than 1 gpu on my mobo. then whats the use of a 2nd PCI-E x16?

[whispous]

Adding other PCIe cards that do something else and are 16x length

 

[Average Nerd]

40 minutes ago, EzioWar said:

Hi, i see many mobos have two PCI-E x16 slots, where primary PCI-E x16 is for my gpu, but 2nd one only supports upto X4 or something. I'll never use more than 1 gpu on my mobo. then whats the use of a 2nd PCI-E x16?

You can connect cards in there that use a larger interface than PCIe x1, like HBA cards or high speed network cards.

For example, I need the second x16 slot in my folding rig to hook up a second GPU once the new PSU arrives.

[will0hlep]

31 minutes ago, EzioWar said:

Hi, i see many mobos have two PCI-E x16 slots, where primary PCI-E x16 is for my gpu, but 2nd one only supports upto X4 or something. I'll never use more than 1 gpu on my mobo. then whats the use of a 2nd PCI-E x16?

I just bought a B550 Taichi exactly because it has a second PCI-E x16 slot (that runs at x8)

13 minutes ago, Average Nerd said:

You can connect cards in there that use a larger interface than PCIe x1, like HBA cards or high speed network cards.

Just as average nerd points out: I need it connect a HBA card in my NAS (allows you to connect up a ton of HDDs).

 

My main machine also has the same feature and my plan is to install 10Gbe at a later date.

I think I will be using 3 PCIe slots in all 3 of my machines very soon.

My main: GPU (x16), 10Gbe card (tba) (x4), TV Tuner card (x1)
My NAS: GPU (x16), 10Gbe card (currently 2.5Gbe) (x4), HBA (x8)
My second machine: GPU (x16), Capture Card (x4), 2.5Gbe card (x1)

[GuiltySpark_]

Plenty of uses, as have been outlined already, but many people have no use for anything beyond the first slot, myself included. Simply depends on what you need/want the PC to do.