There are three common types of PCI-E including PCI-E 1.0, 2.0 and 3.0.
PCI-E 1.0: The maximum theoretical data transfer rate is up to 250MB/s.
PCI-E 2.0: The maximum theoretical data transfer rate is up to 500MB/s.
PCI-E 3.0: The maximum theoretical data transfer rate is up to 1GB/s.
If the data transfer rate of the device is under 250MB/s, please check the motherboard first to see if the slot is PCI-E 2.0.