Caporegime
The fact that AMD went with a two stack solution, indicates they must have made some decent improvements to utilising memory bandwidth more effectively over Fiji,as the core will be faster especially if the 40% to 50% increase in clockspeeds are accurate.
Edit!!
Also the Vega uarch is now confirmed for use in the AMD Ryzen APUs,so that means it needs to be more effective in utilising memory bandwidth and needs to be lower power than what AMD has now. These are the two areas which limited performance on AMD IGPs,ie,the ability to maintain decentish clockspeeds in TDP limited environments and the memory bandwidth required for the IGP.
Edit!!
Also the Vega uarch is now confirmed for use in the AMD Ryzen APUs,so that means it needs to be more effective in utilising memory bandwidth and needs to be lower power than what AMD has now. These are the two areas which limited performance on AMD IGPs,ie,the ability to maintain decentish clockspeeds in TDP limited environments and the memory bandwidth required for the IGP.