I wonder why they do not make more memory channels to get more performance out of the iGPU. 3 or 4 channels would be better than two. They could even allow segregation of traffic or memory QoS.
There's a rumor that AMD is going to do that next year for their high-end mobile chip: double the memory bus size to 256 bit, and bump the iGPU CUs from 12 to 40!