MOORE'S LAW, the observation that the number of transistors on an integrated circuit doubles around every two years, is due to be revoked by 2021 as copper on silicon technology reaches its practical limits.
Moore's Law has been pretty accurate since it was coined by Fairchild Semiconductor and Intel co-founder Gordon Moore in a 1965 research paper, confounding sceptics who expected progress to slow as integrated circuits shrank with each successive generation.
But the latest roadmap (PDF) from the Semiconductor Industry Association (SIA) indicates a change in as early as 2021. The SIA said that even if it is physically possible for chip makers to cram in a few more transistors, it will probably not be financially practical because of the huge costs of manufacture.
The roadmap runs until 2030, and is described by SIA president and CEO John Neuffer as the "final instalment".
"Each new technology generation produces faster transistors that can switch faster than those produced with the previous technology generation," said the report.
"In the past, this electrical feature of transistors enabled microprocessors to operate at higher frequencies and, therefore, computer performance as measured by industry benchmarks."
But computers' fundamental underlying architecture hasn't changed since Hungarian-American mathematician and computer scientist John von Neumann introduced the various core concepts in 1945.
Until around 2000, each proceeding generation of microprocessors increased in terms of performance and power consumption until fundamental thermal limits were reached. That is to say, heat generation became an increasing problem.
"Even though the transistor count has kept on increasing ... at Moore's Law pace, and transistors are able to operate with each new technology generation at higher frequencies than before, it has become practically impossible to keep on conjunctly increasing both of these factors due to physical limitations on power dissipation," said the SIA.
"One of the two features (number of transistors or frequency) had to level off in order to make the integrated circuits capable to operate under practical thermal conditions. Frequency was selected as the sacrificial victim and it has stalled in the few gigahertz since the middle of the previous decade."
As a result, the computer industry "has been compelled to develop such methods as complex software algorithms and clever instruction management to improve performance to partially compensate".
At the same time, the rise of mobile has placed the emphasis squarely on reducing power consumption, and chip makers have increasingly struggled to shrink their integrated circuits - from 28nm to 14nm and, soon, to 10nm. The practical limit in terms of integrated circuits will be reached at around 6nm, if that is financially practical to achieve.
"Geometrical scaling characterised the 1970s, 1980s and 1990s. This was the first generation of transistor scaling. Major material and structural limitations were identified in the mid-90s, and the research community initiated the foundation of a new scaling approach that was heralded by the International Technology Roadmap for Semiconductors in 1998. This was named Equivalent Scaling," said the report.
"Strained silicon, high-k/Metal gate, FinFET and the use of other semiconductor material (for example, germanium) represent the main features of this scaling approach. As features approach the 10nm range and below it becomes clear that the semiconductor industry is running out of horizontal space."
The SIA anticipates memory, and flash memory in particular, to lead the way for microprocessor technology, while chip makers will increasingly resort to techniques such as 3D packaging and 3D chips which stack silicon layer on layer. µ
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