Does NVIDIA Tegra SoC's and AMD Fusion APU's bypass the GPUCPU memory transfer bottleneck?
Well I know that Intel somehow solved this problem by placing the GPU into the same NUMA switching complex as the CPU cores. This is implied from Intel Xeon E3-12x0v3/12x1v3 specs indicating for those Xeon E3-1200s with i7-compatible sockets but no GPU, the memory bandwidth that was used by GPU on i7s and E3-12x5v3/12x6v3 is made available to the CPU cores.

This does suggest that the shared L2 and L3 cache on Intel processors is available to both CPU cores and built-in GPU cores. So as long as the data fit in cache, no main memory access is needed.