PCI Express x4 network card into PCI-Express x16 slot?

A PCIe card and mainboard will negotiate the connection to the fastest supported by both So a x4 card will fully utilize a x4 slot

PCIe cards can always operate in PCIe slots with the same or more lanes than the card For example, an x8 card can operate in a slot with x8, x16, or x32 lanes

candy stars slot Making sure Graphics Card is running at pcie x16 speeds in bios & Windows

can i use pcie 30 in 20 slot If you have a board that does not do CrossfireSLI, then sticking a card into another slot will have no bearing on the first You could also get an enthusiast