From the Blog:
The Real Purpose of the CPU
The most important question a CPU designer must ask himself or herself is, what is the purpose of the CPU? Most people in the business will immediately answer that the purpose of the CPU is to execute sequences of coded instructions. Sorry, this is the wrong answer. This definition is precisely what got us in the mess that we are in. In order to figure out the answer to this crucial question, we must first grok the true nature of computing. And the sooner we learn that a computer is really a collection of concurrently behaving and communicating entities, the sooner it will dawn on us that the CPU is a necessary evil.
Necessary Evil
Why necessary evil? Because, ideally, each and every elementary entity in a computer should be its own self-processor, not unlike a neuron in a biological nervous system that sits around most of the time waiting for a signal to do something. In other words, ideally speaking, additions should add by themselves and multiplications should multilply by themselves. Unfortunately, we have not yet progressed to the point where we can build super-parallel systems like the brain with its tens of billions of tiny, interconnected, self-executing processors. That will come one day, but not today.
CPU as Simulator
Fortunately, what we lack in numbers, we make up in speed. We can have a single fast CPU do the work of thousands or even millions of elementary processors (cells). Ideally, adding more CPUs or cores into the mix should improve performance linearly. At least, that is the goal. So this, then, is the true purpose of the CPU, to simulate the behavior of a large number of behaving and inter-communicating cells. So, essentially, the CPU is a cell simulator, or cell processor if you wish. If the reader disagrees with my argument so far, there is no point in reading any further because what I am going to say below depends on what I said above.