Difference between high overhead and low overhead in games, on AMD GPUs. That is pretty amazing. 30% performance boost between Windows 10 and Windows 8.1. Metal will equal the performance of DirectX, so we can say, that Apple could be dead right with their 50% optimization of performance of hardware. Test is on R9 280X, which is in fact Tahiti GPU - the same core which is in Mac Pro's D700. I would say: its completely mental.