Actually, it's a combination of both, because the CPU/GPU are an APU. The GPU is a combination of two Radeons, one which handles it, one which ... might. The CPU also clocks down and up based on need, so the CPU component can deadlock and the GPU component may use the wrong one to create a context, or give the wrong context on a late redetection.

From a developer point of view, Fusions are a nightmare (and I say this only dealing with 2D office applications from a support role who reads tech docs to determine outcomes for people with issues on things with minimal hardware acceleration!). The fusions are good in theory for basic desktop publishing, but their impact on the gaming industry will be perverse.