As for Cape Verde itself, as our regular readers may already know, it’s one of AMD’s first-generation GCN 1.0 GPUs, launched back in 2012. Compared to the GK107 GPU found in the GT 750M, it is a larger, more powerful (and at least in the desktop, more power-hungry) GPU, designed for more powerful devices than GK107 was. As for why Apple opted to switch now and to this GPU, we’ll leave that to Apple, AMD, and NVIDIA, though it’s by no means surprising that after having run GK107 for a couple of years, they would want to upgrade to a more powerful GPU.
Meanwhile, though we don’t have M370X on-hand at the moment, at least in the desktop, where GPU performance is unrestricted by thermals, Cape Verde fares very well. The rMBP on the other hand does have thermal constraints to deal with, so performance won’t be the same, but I expect it to fare reasonably well as well. Though at the same time I’m also curious if the use of a higher performance part has impacted the rMBP’s battery life when the dGPU is active; AMD and NVIDIA both do heavy binning, so a simple extrapolation won’t work here.