[erik]

Re:your edit, the PCIe lane configurations from the CPU aren't that flexible. There is no 4x+4x+4x+2x+1x+1x configuration.

4x Thunderbolt + 4x Thunderbolt + 8x GPU, with everything else on the PCH would make sense for the 15". Or maybe they connected the SSD (also 4x PCIe) to the CPU, and one of the Thunderbolt controllers to the PCH.

Hopefully they used the full set of CPU lanes. Most laptop manufacturers have a tendency to under utilize the CPU lanes and put things on the bandwidth constrained PCH for some reason.

[tmzt]

This feels like something Steve would not have let out the door, those kind of rules should never be the customer's concern.

[Decade]

Yes, he did. As nsxwolf commented, the 2010 MacBook Pro had USB 2 ports that ran at different speeds. And I remember vaguely that that wasn’t the first time.

It’s just not your problem because, really, how many people are going to be inconvenienced by the right Thunderbolt ports being slightly slower than the left Thunderbolt ports?