A little from column A and a little from column B, but assuming column B is more cores, then more column B than A... the problem with silicon is not just heat but also that as they pack more transistors into the same space, they need to shrink the manufacturing process, this results in more wasted silicon as well as there currently being a physical limit to how small a track of silicon can be before it simply breaks down when a current is passsed through it (cant remember the exact figure but it isnt far from the 45nm we are currently working at). There are people looking at how to alter silicon to become more resistant, and of course what new materials we could use, but at the moment I dont see anything so compelling that I would place all my chips on it.
In the long run, Its not just multiple CISC cores that the big boys are concentrating on, rather they are more likely to produce Cell style processors, even Intel.
Even now, their "lab baby" is an 80 core Cell style processor. In a similar manner to a GPU it has 80 individual simple processing "cores", each has a pre-determined processing task it is designed for and isn't astonishingly fast in itself. But as a conglomerate the processing potential of the chip is very high.
Like processing on the GPU (CUDA, OpenCL etc), they are also looking at how to best utilise this parallelism, using things like hardware thread schedulers. In theory meaning the programmer becomes detached from how their work is being parallelised once more (people dont like programming in parallel, its a bit of a PITA
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The nice thing of course is that each of these "cores" can pump through data at a slower rate than say a 3Ghz core2 does at the moment, which means they can be made smaller, which means more can be packed into the same die space.
I am almost 100% convinced massive parallelism is the way forward nd what we will see the big players starting to really sell soon. no doubt though that they will continue to push the boundaries of the more traditional multi core CISC processors, i reckon they will progress to at least 8 CISC cores before they turn down their next path.
Watch out for GPU processing as well, NVIDIA is really pushing the concept of using their chips for processing at the moment, and big players like Adobe have begun to pick up on it, expect to see new versions of photoshop with either CUDA or OpenCL support soon i reckon, there is definately something compelling about having a dedicated highly parallelised processing engine within a host system that is there purely to accept high load computation from the host machine. Specially given the cost of the mass produced cards...