AMD Fusion how can CPU and GPU share the same memory?

AMD announced it's Fusion platform some time ago. Having read a bit about it I'm both excited and s开发者_JS百科ceptic. For example it should make it possible that GPUs and CPUs share the same memory. (and the GPU and CPU are both in the same package) Now since GPUs have a much higher memory bandwidth (around 10x the bandwidth a CPU has) and that the way CPUs and GPUs use cache is fundamentally different, the question arises how the heck can they do this? I wonder if any details are known.

I have also searched for some detailed info on how this APU technically works, but haven't found anything better than AMD's whitepaper on the subject, which, in a slightly marketing-wise tone, does present a lot of good info.

By using high-bandwidth dual ported RAM. AMD is happy to explain.

Here is a good paper (from AMD) explaining the different memory access patterns in an APU http://amddevcentral.com/afds/assets/presentations/1004_final.pdf

CPUs and GPUs have been sharing memory for years. Fusion is no different, in fact it's far from the first instance of a GPU being integrated into a general-purpose CPU core.

Like all other such solutions, it'll be fine for casual use, but it'll be far from cutting-edge 3D acceleration.