What is Moore’s Law?

Moore’s Law is kind of like the law of rabbit reproduction . . .

First, there are two rabbits on an island. The next day there are four, then eight, then 16, 32, 64, 128, 256, and so on. Soon enough, the island is completely overrun by rabbits, because they reproduce at an exponential rate. Similarly, according to Moore’s Law, the number of components in a computer chip grows at an exponential pace: It doubles every two years.

Moore’s Law is an observation that the number of transistors in a computer chip doubles every two years or so. As the number of transistors increases, so does processing power. The law also states that, as the number of transistors increases, the cost per transistor falls. So not only will the processing power of computer chips grow exponentially, but the cost per transistor will also decline exponentially.

For example, in 1993, the Intel Pentium processor had 3.1M transistors. Two years later, the new version of the same processor had 5.5M transistors. By 2003, the number of transistors had jumped to 55M.

For the past five decades, Moore’s Law has accurately predicted developments in computer technology. In the 55 years since Moore first made his prediction, processors have gone from 3,500 transistors per chip to close to 50B. But this law will likely hit a wall eventually. At a certain point, transistors will become so small that the effects of quantum physics will prevent them from functioning properly. When Moore’s Law comes to an end, there may be a severe slowdown in computer hardware growth, which has some computer scientists and economists worried.

In 1965, American engineer Gordon Moore, who went on to co-found Intel, wrote an article for the journal Electronics about his technological forecasts for the coming decade. He predicted that the number of transistors in a computer chip would double every year, reaching 65,000 by 1975.

Moore wrote that this exponential growth in computing power would “lead to such wonders as home computers — or at least terminals connected to a central computer — automatic controls for automobiles, and personal portable communications equipment.”

Moore’s Law helped rally interest in the emerging computer and semiconductor industries and gave this new space a plan of action: Keep squeezing more transistors into chips, and eventually, people will get access to home computing and all the modern tools we rely on today. Soon, computer engineers were making it a goal to stay in line with Moore’s Law.

In 1975, Moore revised his prediction based on new data, stating that processing power would double every two years instead. This prediction has held true (although been a bit too pessimistic), with the number of transistors doubling approximately every 18 months over the five decades since 1961. Computer scientists and engineers have used Moore’s Law as a roadmap, trying to stay on track so that society can enjoy the many technological wonders Moore predicted.

But advances in computer processing power have begun to slow down in recent years, and experts predict that Moore’s Law will no longer be valid sometime soon. As chip components become increasingly smaller, the bizarre effects of quantum mechanics start to prevent them from working properly. That may mean new technologies beyond today’s silicon and transistors will be necessary to continue moving computer technology forward.

Moore did not make an equation for his prediction, but it’s easy to create one. One of the simplest is:

Future Processing Power = Current Processing Power ⋅ 2n

In which n = the number of years to develop a new microprocessor divided by 2.

Let’s do a quick example. In 1972, the Intel 8008 had 3,500 transistors. What is the expected number of transistors in 10 years (1982)?

Future Processing Power = 3,500 ⋅ 25

After doing the calculation, we see that:

Future Processing Power = 112,000

In 1982, Intel released the 286 processor, which featured 134,000 transistors — only slightly more than Moore’s Law predicts.

Moore’s Law originally predicted that the number of transistors in a processor would double every year (he later revised it to every two years). The law applies to integrated circuits (a piece of semiconducting material with several circuits on it) and the technologies that use them.

Moore believed that as computing power increased, the cost per component would decrease, eventually making the technologies that are so integral to our lives — like smartphones and laptops — not only possible, but affordable.

It is not entirely clear whether Moore’s Law is still valid. There have been conflicting signs as to whether the growth in processing power has been slowing down. For example, in 2016, Intel announced that it would not be releasing new chip technologies as quickly as it did in the past. But soon after, the company announced that it had overcome roadblocks and was now back on track with Moore’s Law.

Regardless of whether it’s still valid at the moment, computer scientists are becoming increasingly concerned that Moore’s Law will soon lose its predictive ability. At a certain point, transistors will become so small that the effects of quantum mechanics will make increasing processing speeds harder than before.

Although Moore’s Law has made accurate predictions since it was first introduced, it appears inevitable that it won’t be valid forever.

When Moore first made his prediction, transistors were much larger than they are now. As they’ve shrunk, they are beginning to encounter new roadblocks: the effects of quantum mechanics.

Quantum mechanics is a branch of physics that describes the behavior of subatomic particles. Oddly enough, the effects of quantum mechanics don’t emerge above a certain size. But as transistors begin to cross that threshold, they’re finding themselves subject to all the strange rules that make quantum mechanics so counterintuitive for most people.

For example, quantum tunneling lets electrons jump from one place to another, or “tunnel through” something. For a computer chip, this can impair its functioning. Processors rely on logic gates, components that either allow or block the movements of electrons, to work. If electrons can simply tunnel through (bypass) logic gates at the quantum level, then the processor won’t be able to function properly.

These issues set a physical roadblock for the continuation of Moore’s Law. It seems that at a certain point, cramming more components onto integrated circuits simply won’t cut it. Instead, computer engineers may need to come up with an alternative to the standard silicon semiconductor chip, like quantum computers.