[revelation]

Full Thunderbolt 3 for all four ports on the 15"?

I mean, I'm not sure how you can get 40 GBit/s with 4x PCIE 3.0 in the first place, every quote I find says 32 GBit/s. Maybe there is that much overhead in Thunderbolt.

But surely 4x40 Gbit/s would require 16 lanes at least. I don't think Intel makes any consumer CPUs with more than 16.

[erik]

The 40 GBit/s is definitely confusing.

My understanding is that that's total bandwidth across all protocols. So the mix of Displayport and PCIe 3.0 can't exceed 40 GBit/s. The 4x PCIe 3.0 on it's own is 32 Gbit/s, as you mentioned.

Each controller provides two Thunderbolt ports, which share bandwidth. For the 15", 4x PCIe to the left side Thunderbolt controller, 4x PCIe to the right side Thunderbolt controller, and 8x to the GPU would be a sensible configuration. Though who knows if Apple took this approach.

[Klathmon]

What do you mean by consumer CPUs?

I've got an ivybridge i7 with 40 lanes right now in my system.

[danudey]

4x PCIe 3.0 (~30Gbit) + USB 3.1 Gen 2 (10 Gbit) = the 40 GBit number quoted.