We mentioned that each QuickPath Interconnect lane is 20-bit wide. What we didn’t mention is that QuickPath allows each lane to be treated as being four 5-bit lanes. This division is available for improving reliability especially on the server market environment. You won’t see this feature being implemented on desktops.
When this feature is implemented, if the receiver perceives that the connection between it and the transmitter is physically damaged, it can shut down the portion of the bus that is damaged and operate transmitting fewer bits per time. This will of course lower the transfer rate but at the other hand the system won’t fail, what wouldn’t happen on a system not implementing this feature.