Great answer cjl - thanks! How would someone know when an extra 2 bits is included for parity checking? So it applies to SATA but what about other transfer rates for storage devices? How would you know?
It depends on the specific connection used. 8b/10b encoding is quite common though - USB, FireWire, gigabit ethernet, PCI-E, and HyperTransport all use it as well for example (and that's not even close to a complete list).