Sure, but that's because you're using 4 channels to get there and it's unidirectional. Thunderbolt is 10 Gbps per channel, so actually up to 40 Gbps if there we

Sure, but that's because you're using 4 channels to get there and it's unidirectional. Thunderbolt is 10 Gbps per channel, so actually up to 40 Gbps if there were 4 channels available (there are only 2 shipping on the MacBooks, hence the 10Gbps bi-directional rating).