the rise and dominance of the general-purpose personal computer. The success of the general-purpose microcomputer, which has been due primarily to economies of scale, has had a devastating effect on the development of alternative computer and programming models. The effect can be seen in high-end machines like supercomputers and in low-end consumer devices, such as media processors. Even though alternative architectures and approaches might have been technically superior for the task they were built for, they could not easily compete in the marketplace and were readily overtaken by the ever-improving general-purpose processors available at a relatively low cost. Hence, the personal computer has been dubbed “the killer micro.”

Over the years, we have seen a series of revolutions in computer architecture, starting with the main-frame, the minicomputer, and the work station and leading to the personal computer. Today, we are on the verge of a new generation of smart phones, which perform many of the applications that we run on personal computers and take advantage of network-accessible computing platforms (cloud computing) when needed. With each iteration, the machines have been lower in cost per performance and capability, and this has broadened the user base. The economies of scale have meant that as the per-unit cost of the machine has continued to decrease, the size of the computer industry has kept growing because more people and companies have bought more computers. Perhaps even more important, general-purpose single processors—which all these generations of architectures have taken advantage of—can be programmed by using the same simple, sequential programming abstraction at root. As a result, software investment on this model has accumulated over the years and has led to the de facto standardization of one instruction set, the Intel x86 architecture, and to the dominance of one desktop operating system, Microsoft Windows.

The committee believes that the slowing in the exponential growth in computing performance, while posing great risk, may also create a tremendous opportunity for innovation in diverse hardware and software infrastructures that excel as measured by other characteristics, such as low power consumption and delivery of throughput cycles. In addition, the use of the computer has becomes so pervasive that it is now economical to have many more varieties of computers. Thus, there are opportunities for major changes in system architectures, such as those exemplified by the emergence of powerful distributed, embedded devices, that together will create a truly ubiquitous and invisible computer fabric. Investment in whole-system research is needed to lay the foundation of the computing environment for the next generation. See Figure 2.1 for a graph showing flattening curves of performance, power, and frequency.

Traditionally, computer architects have focused on the goal of creating



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