Modern computers have at their heart a piece of equipment commonly referred to as the "Central Processing Unit" (CPU). This is common knowledge and regularly used as the final determinant factor in a computer's performance. The reality of a machine's performance, however, is a much more complicated equation. Like many devices, the overall performance is a measure of the sum of parts that compose the system. Similarly, a single poorly performing component can undermine, or even negate, the performance of the other components. Using blindingly fast CPU's in a system with very slow memory will result in a computer that is well below accepted standards. However, fast components are becoming very cheap and offer other advantages beyond the initial design goals of the component in question.
For instance, most people are unaware that their video card has a highly specialised processor call a "Graphics Processing Unit" (GPU). The GPU, unlike the CPU is designed for a set of very specific calculations; usually matrix transformations using arbitrarily precise floating point numbers - usually double precision floating points, but not always. The GPU typically runs at a slower clock speed than the CPU and uses a very fast, purpose-built memory subsystem of its own too. Combined, the video card's GPU and memory are capable of some truly mind-boggling calculations. Here's where things get interesting; many facets of science and "non-graphic" mathematics use exactly the same type of calculations the GPU was designed for. In fact nVidia has even released a programming framework (called CUDA) to leverage their GPU's for doing things other than playing games. Researchers in Belgium at the University of Antwerp, have now been able to build a system, capable of super-computer speeds, using commodity graphics cards totalling eight GPU's!
For quite some time now, I've considered the role of the general purpose microprocessor, aka CPU, rather limiting. As stated before, a single component doesn't in itself determine how fast a machine will be, but a single component can certainly determine how slow a machine will be. I believe the time is coming when to move beyond current performance limitations, the computer industry will need to utilise specialised processors for specialised tasks. Given the generalist role a CPU must undertake, by design it is a compromise to balance performance across a broad set of tasks, consequently it will never excel at any specific task. However, if the CPU could offload particular tasks to other, external, processing units specialised for that particular task the overall performance of the system would increase significantly. We have already seen this in limited ways with the advent of hardware-based storage controllers, dedicated graphics processors and I would argue the advent of the northbridge for direct access to various busses that link the core of the system together. Prior to the separation of the CPU and northbridge, all input and output (I/O) to any device was forced to go through the CPU. With northbridge controller the CPU could be freed up and many devices are capable of direct communication and data transfer.
In conclusion, I look forward to future of the CPU; whether it's a Intel "Core", IBM "Cell" or any other processor. However, what really interests me, is the rise of the specialist processor and how we as programmers and system engineers can find new and innovative ways to implement them to augment and enhance overall system performance in specialised ways.