Also from what I've heard the GPU(s) are underclocked . There seems to be a fix for MacBooks with dedicated gpu .
Looks like removing AppleGraphicsPowerManagement.kext fixes the issue :
https://forums.macrumors.com/threads/1386070/
"While Googling I found a tip regarding lagginess in Lion (not retina related) that suggested disabling System/Library/Extensions/AppleGraphicsPowerManagement.kext. Tried that, and it does make a noticeable different, albeit at the expense of additional heat and noise. It appears Apple very aggressively throttles the GPU to keep heat and fan noise down on the desktop. When I run xbench UI test (yeah, I know, xbench sucks) the numbers go from ~90 (with AGPM) to ~180 (without AGPM), so about double the performance.
It seems we only get full graphics performance with games that directly address hardware.
Note: I am running the GT650, not internal."
Could anyone try this ? On my macbook with intel iris has no effect .