AMD have recently been building chips with the CPU and the GPU on the same die. Kaveri takes this one step further and allows the CPU and the GPU to access the same memory, hence reducing the time required to pass data from the CPU to GPU and back again. AMD call this "Heterogeneous Uniform Memory Access" or hUMA for short.
To quote AMD:
"Game developers and other 3D rendering programs have wanted to use extremely large textures for a number of years and they've had to go through a lot of tricks to pack pieces of textures into smaller textures, or split the textures into smaller textures, because of problems with the legacy memory model... Today, a whole texture has to be locked down in physical memory before the GPU is allowed to touch any part of it. If the GPU is only going to touch a small part of it, you'd like to only bring those pages into physical memory and therefore be able to accommodate other large textures."
It's only hUMA
"With a hUMA approach to 3D rendering, applications will be able to code much more naturally with large textures and yet not run out of physical memory, because only the real working set will be brought into physical memory."
AMD are members of the Heterogeneous System Architecture (or HSA) foundation, whose other members include ARM, Samsung, Texas Instruments and Qualcomm.
Interestingly, AMD are providing the processors for the new Playstation 4 and possibly for the XBOX 720 as well. These system could well be using hUMA technology.