Confused About What PCIe2 Slots Are Compatible

I own Asrock 990 FX Extreme 3 and I'm sure I put graphic card in X16 slot,it's in PCIE2 slot But why is it running in X4 mode,and how to

The PIXCI® mf2280 for the M 2280 length slot is now available Please PCIe x4 Camera Link Frame Grabber SILICON VIDEO® 1820 · SILICON VIDEO

speaker with pendrive slot Two types of PCIe slot on an Asus H81M-K motherboard Various slots on a computer motherboard, from top to bottom: PCI Express x4; PCI Express x16; PCI Express

slot con rtp alto Since this statement is referring to the two port model, I am wondering if the single port model will run at full speed in a x4 slot 3