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In 1965, Gordon Moore proposed that the number of transistors on a silicon chip would double every year. Moore’s Law, as it is now known, proved prophetic about the exponential growth of computing power that made much of the modern world possible.
Starting around 2010, however, Moore’s Law began to break down and many today are asking if our age of unprecedented growth is coming to an end.
A Small Transistor
Gordon Moore is the co-founder of the Intel Corporation and one of the men largely responsible for the computer age.
His work with the silicon transistor began in 1956, when he went to work for the transistor’s inventor William Shockley and he has been inseperable from the transistor ever since.
A transistor produces, amplifies, and directs an electrical signal using three leads, a source, a gate, and a drain.
When voltage is applied to the gate lead, an incoming current at the source lead will be allowed to pass through to the drain lead. Take the voltage away from the gate lead and the current cannot pass through.
What this does is produce a way to compute logical values, 1 and 0 in computer terms, based on the whether there is voltage applied to the gate and the source leads.
Connect the drain lead of a transistor to the source lead or the gate lead of another transistor and suddenly you can start producing incredibly complex logic systems.
Comparable to the neuron of the human brain, this network of transistors is responsible for the functioning of nearly all modern devices, from a digital alarm clock to a supercomputer.
And the more transistors you can fit on a chip, the more computationally powerful this network becomes.
So when Moore was asked to submit a paper to the journal Electronics predicting the future of technology, he reviewed the data on Fairchild’s production of silicon chips.
He found that the number of transistors on a silicon chip doubled every year and proposed in his paper in Electronics that this rate of growth would continue, later revising this to a more conservative doubling every 2 years in 1975.
While not a law in the mathematical sense, Moore’s Law bore out: about every 18 months, a transistor would be half the size of the current transistor.
This meant more transistors could be packed into a chip, which drove the exponential growth of computing power for the next 40 years.
Why is Moore’s Law Breaking Down?
There are three major factors contributing to the slowing rate of growth in processor power, and they’re all related.
First, you have electrical leakage. For decades, as transistors got smaller, they became more energy efficient.
Now, however, they have gotten so small, as small as 10 nanometers, that the channel that carries the electrical current through the transistor cannot always contain it.
This generates heat which can wear out the transistors more quickly, making them even more susceptible to leakage.
Heat isn’t just limited to one transistor though.
Billions of transistors leaking can seriously threaten the integrity of the whole chip, so the processor must reduce the amount of voltage it takes in or throttle the number of transistors in use to prevent overheating, limiting the processing power of the chip.
Finally, there is the third strike against Moore’s law: economics.
When the number of transistors doubles, so does the amount of heat they can generate. The cost of cooling large server rooms is getting more and more untenable for many businesses who are the biggest purchasers of the most advanced processing chips.
As businesses try to extend the life and performance of their current equipment to save money, chipmakers responsible for fulfilling Moore’s Law bring in less revenue to devote to R&D—which itself is becoming more expensive.
Without that extra revenue, it becomes much harder to overcome all of the physical impediments to shrinking the transistors even further.
So, it might not be the physical challenges that bring an end to Moore’s Law, but simply the lack of demand for smaller transistors.
Progress by Other Means
Chipmakers and manufacturers have known about this challenge to Moore’s Law for at least a decade.
As such, they have been finding ways to continue the growth in computing power without needing to solely rely on smaller transistors every two years.
There have been advances in alternative models for transistors that have shown promise.
Both multigate and Tri-gate transistor models offer ways to extend Moore’s law for a time and are already being used in many electronic devices.
But all these can do is extend the effective life of Moore’s Law.
One of the earliest and most effective approaches to this problem was the adoption of multiprocessor and multicore architectures.
If you want more power from a chip that has come to the limits of its capacity, use two or more chips instead of one and you can continue increasing your processing power, though at greater power consumption cost.
Multicore systems meanwhile use a processor design that features several execution cores in a single processor.
Each core is less powerful than the previous generation’s single core design, but several smaller chips can be used more concurrently and efficiently and give an effective increase in computing power.
Moore’s Law is Dead. Long Live Moore’s Law!
The end of Moore’s Law as we know it was always inevitable. There is a physical limit to what can fit on a silicon chip once you start working with nanometers.
Go any smaller and you start dealing with subatomic particles which immediately puts you in the realm of quantum computing, which is where we’re already headed.
One day though, after the transistor get stuck at three atoms and an electron, someone will notice that the computation power of newer forms of transistors are rapidly advancing.
Molecular, DNA, or Spintronic transistors will appear to pick up where silicon left off and Moore’s Law will be brought out of retirement until quantum computing makes discussions about limits irrelevant.
Ultimately, this has had less to do with transistors than it has to do with us as a society. Our hope and expectations for progress won’t end with the final generation of silicon transistors because we won’t let it.
We will find a way to bring Moore’s Law back, for whatever else comes after, simply because we want it to be true.