Q:

How can PCI-E 4x network card support 10GB/s speed?

This card https://www.edimax.com/edimax/merchandise/merchandise_detail/data/edimax/global/smb_network_adapters_pci_card/en-9320tx-e/
Manufacturer claim this is 10GB/s card:

10 Gigabit throughput with 100-meter UTP cable
PCI Express rev. 2.0 Specification x4 interface

Now wikipedia say, that 4x PCI-E slot revision 2 supports max 2.0 GB/s bandwidth. So how is this card supposed to work? Is the wikipedia wrong? Or manufacturer lying? Or is there some black magic I am not aware of?
https://en.wikipedia.org/wiki/PCI_Express

A:

They are in different units.
The network card is advertised in Gigabits/s (Gb/s), whereas the PCI-E wikipedia page shows the speed in Gigabytes/s (GB/s). 1 Gigabyte = 8 Gigabits or 1GB = 8Gb.
So the 4X PCI-E rev.2 actually supports 16Gb/s, which is more than enough to handle the 10GbE card.
(if you check the manufacturer's site, only Gb is used, not GB, as misquoted in the question)

A:

You are mixing up gigabit and gigabytes.
2 gigabytes per second (GB/s) is 16 gigabits per second (Gb/s). Hence the PCIe x4 slot can easily support 10 gigabit with, in theory, 6Gb/s spare.

