【正文】 igners began to experiment with new architectural features designed to give extra speed. One very successful experiment concerned methods for predicting the way program branches would go. It was a surprise to me how successful this was. It led to a significant speeding up of program execution and other forms of prediction followed Equally surprising is what it has been found possible to put on a single chip puter by way of advanced features. For example, features that had been developed for the IBM Model giant puter at the top of the System 360 now to be found on microputers Murphy’s Law remained in a state of suspension. No longer did it make sense to build experimental puters out of chips with a small scale of integration, such as that provided by the 7400 series. People who wanted to do hardware research at the circuit level had no option but to design chips and seek for ways to get them made. For a time, this was possible, if not easy Unfortunately, there has since been a dramatic increase in the cost of maki ng chips, mainly because of the increased cost of making masks for lithography, a photographic process used in the manufacture of chips. It has, in consequence, again bee very difficult to finance the making of research chips, and this is a currently cause for some concern. The Semiconductor Road Map The extensive research and development work underlying the above advances has been made possible by a remarkable cooperative effort on the part of the international semiconductor industry. At one time US monopoly laws would probably have made it illegal for US panies to participate in such an effort. However about 1980 significant and far reaching changes took place in the laws. The concept of prepetitive research was introduced. Companies can now collaborate at the prepetitive stage and later go on to develop products of their own in the regular petitive manner. The agent by which the prepetitive research in the semiconductor industry is managed is known as the Semiconductor Industry Association (SIA). This has been active as a US organisation since 1992 and it became international in 1998. Membership is open to any organisation that can contribute to the research effort. Every two years SIA produces a new version of a document known as the International Technological Roadmap for Semiconductors (ITRS), with an update in the intermediate years. The first volume bearing the title ‘Roadmap’ was issued in 1994 but two reports, written in 1992 and distributed in 1993, are regarded as the true beginning of the series. Successive roadmaps aim at providing the best available industrial consensus on the way that the industry should move forward. They set out in great a 15 year horizon. the targets that must be achieved if the number of ponents on a chip is to be doubled every eighteen is, if Moore’s law is to be if the cost per chip is to fall. In the case of some items, the way ahead is clear. In others, manufacturing problems are foreseen and solutions to them are known, although not yet fully worked out。 see in particular Computer Architecture, third edition, 2020, pp 146, 1514, 1578. The IA64 instruction set. Some time ago, Intel and HewlettPackard introduced the IA64 instruction set. This was primarily intended to meet a generally recognised need for a 64 bit address space. In this, it followed the lead of the designers of the MIPS R4000 and Alpha. However one would have thought that Intel would have stressed patibility with the x86。 it had always been that way. This was what I meant when I referred in my abstract to inflation in the puter industry ‘going the other way’. As time goes on people get more for their money, not less. Research in Computer Hardware. The time that I am describing was a wonderful one for research in puter hardware. The user of the 7400 series could work at the gate and flipflop level and yet the overall level of integration was sufficient to give a degree of reliability far above that of discreet transistors. The researcher, in a university or elsewhere, could build any digital device that a fertile imagination could conjure up. In the Computer Laboratory we built the Cambridge CAP, a fullscale miniputer with fancy capability logic. The 7400 series was still going strong in the mid 1970s and was used for the Cambridge Ring, a pioneering wideband local area work. Publication of the design study for the Ring came just before the announcement of the Ether. Until these two systems appeared, users had mostly been content with teletypebased local area works. Rings need high reliability because, as the pulses go repeatedly round the ring, they must be continually amplified and regenerated. It was the high reliability provided by the 7400 series of chips that gave us the courage needed to embark on the project for the Cambridge Ring. The RISC Movement and Its Aftermath Early puters had simple instruction sets. As time went on designers of mercially available machines added additional features which they thought would improve performance. Few parative measurements were done and on the whole the choice of features depended upon the designer’s intuition. In 1980, the RISC movement that was to change all this broke on the world. The movement opened with a paper by Patterson and Ditzel entitled The Case for the Reduced Instructions Set Computer. Apart from leading to a striking acronym, this title conveys little of the insights into instruction set design which went with the RISC movement, in particular the way it facilitated pipelining, a system whereby several instructions may be in different stages of execution within the processor at the same time. Pipelining was not new, but it was new for small puters The RISC movement benefited greatly from methods which had recentl