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Physical constraints
Microprocessor designers today encounter many difficulties. None of them is not insurmountable, but solutions are becoming heavier. We look at some of them, trying to extrapolate the future impact of these barriers will then suggest solutions to overcome them.
Access memory
As seen in figure ‘Performance – memory and processors, memory speed over the past 10 years has increased by 10% per year, while processor speed has increased at a rate of 60%. All reasons for us to believe that this disparity will continue to grow, and that the relative price of a memory access (measured in clock cycles) will continue to grow.
Power
Another factor limiting the development of integrated circuits is power consumption, 15 years ago with a processor consumes 2 watts, today the Alpha 80364 processor consumes 100W, hence the limitations clock (power consumption increases with clock frequency), and need special cooling devices.
Fortunately technology work towards positive: miniaturization leads to a weakening necessary. Another factor that lowers the power consumption is low supply voltages.
Interestingly, although the size of transistors in a low, increased size circuits manufactured: hunger tireless designers area requires increasingly higher silicon plates, meaning that power consumption increased as well. Complexity
Negligible factor is the enormous complexity of the circuits. Most modern processors have more than 25 million transistors, and in a few years designers will have one billion. Such circuits are very difficult to verify and test. At a company like Intel currently spends 40% of the budget for design and development, and 60% for verification and testing!
Another important issue relates to the technological lines of production: such a facility currently costs two billion U.S. dollars. Few companies can afford the investment of this scale for a technology that is changing in three years!
Wires
It is clear that miniaturization is not going to pace exponentially: over some time I get to need to make a transistor smaller than an atom, which is obviously impossible. But even before reaching such a threshold, we have other problems to face.
A very interesting analysis was made by Mark Horowitz, Stanford University professor, in an article entitled “The Future of wires”. The article is based on the electrical characteristics of semiconductors and analyzing a series of possible scenarios for technology. The text takes into account all sorts of factors, such as wire geometry, capacitors and resistors, power dissipation, etc. We ignore all these details, but we see one of the conclusions the author reaches.
The author notes that in general will evolve in the desired wire: they become shorter and the speed of transmission of information does not fall relative to the size of the circuit. So if we take a microprocessor today, and I scale, wires should not hinder the correct operation.
But the problem arises from the fact that the circuit area does not decrease because the designers add new modules. A big problem is the wires passing through several modules. Their length remains virtually constant, in millimeters. Or, as always clock speed increases, this means that electrical signals do not have time to go through wires from one end to another. At 1GHz, the light passes through the vacuum of 30 inches. But the speed of light is lower in solids and the propagation velocity decreases significantly with the number of “consumers” of wire (ie a wire connected to the three channels is much slower than one coupled to only two). In addition, long transmission lines will need amplifiers, which substantially slow signal.
This means that future circuits will not be able to communicate with global signals: just one wire will be impossible to unite the different parts of the circuit. It is therefore of utmost importance for future architectures!
Noise
Finally, as the transistors are smaller, the wires are thinner and higher power consumption, circuits are more sensitive to noise, be it heat from the environment (eg cosmic rays) or, soon, even quantum effects ! Transport phenomena underlying semiconductor transistor are statistical phenomena: Or, when the dimensions are so small that only a few electrons produce signals not operating statistics and exceptions begin to appear.

Topics: 80364 processor, Alpha, author, Central processing unit, Clock signal, CPU design, Digital electronics, Electronic engineering, Electronics, Engineering, integrated circuits, Intel Corporation, Mark Horowitz, Microprocessor, Professor, semiconductor, Semiconductor devices, semiconductors, Stanford University, technology work, Technology/Internet, Transistor, Transistor–transistor logic, USD

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