A few years back I wrote an N64 emulator graphics module for the Raspberry Pi because I was unhappy with the poor performance of the existing ones and I would have really wanted this. Drawcall overhead for Broadcom's official drivers is extreme: you can't have more than a single-digit number of drawcalls per frame and still maintain 60 FPS. I ended up having to go to ubershaders for everything just to maintain 30 FPS. I'm certain the hardware was capable of much more, but the drivers were holding it back.