This OID reports the maximum PCI Express link speed, in megabits per second, that this device function is capable of, returning 0 if it could not be determined or the device is not PCIe. An admin uses this maximum rating as the baseline to compare against the negotiated link speed, to judge whether a PCIe device is actually running at its full potential. For example, a device with a maximum link speed of 16000 Mb/s that negotiates down to a lower rate would signal to the admin that something is limiting that card below its rated capability.