Understanding Moore's Law: Why Most Computers Become Obsolete After a Few Years


One important factor for anyone buying a computer to consider is how many years of use he might expect to get from his new purchase.  Depending on the hardware in a PC, the useful life can range anywhere from two to five years.  Quite often, any PC over five years old is noticeably slower than most new PCs on the market.  This observable trend is due in large part to what is known as Moore’s law.

What is Moore’s law?

Put simply, Moore’s law states that “the number of transistors on integrated circuits doubles about every two years.”  The law is named after Intel co-founder Gordon Moore, who described the trend in a 1965 editorial published in Electronics magazine.  This trend which Moore predicted has more or less held true since the 1970s through the early 21st century.  More recently, this doubling trend has begun to slow toward the end of 2013.  By 2020, transistor counts and densities are expected to double every three years.  This trend can be seen in the graph below which compares transistor count in processors with the date that they were first introduced to the market.

Transistor Count vs Date of Introduction

What does this all mean?

In practical terms, the potential speed of computer processors doubles about every two to three years.  This explains why the average life of a PC is usually no more than five years.  After five years, a PC’s speed will be slower than a modern PC by a factor of 2x or more.  With software requiring modern computer components to run smoothly, one might encounter problems trying to run new software on a PC that is five or more years old.

Moore’s law is not only applicable to integrated circuits.  Indeed, the capabilities of many digital electronic devices are strongly linked to Moore’s law.  As noted above, processing speed improves at roughly the same rate.  Memory capacity, sensors, and the size of pixels in digital cameras also show similar trends.  Therefore, it is more or less unavoidable for a PC to become obsolete after five years.

There is good news, however.  This doubling trend cannot continue endlessly.  Some forecasts expect Moore’s law to end by as early as 2025.  This prediction is based on some physical hardware limitations.  In physical terms, as the density of transistors on microprocessors increases, it becomes harder to control the current flow through these semi-conductors.  Eventually, the size of a transistor will approach the size of an atom, at which point the size cannot physically be made any smaller.  Another concern is with material properties of circuits.  As electrons move faster and faster through silicon circuits that are becoming smaller and smaller, microchips will get hotter and hotter.  However, microarchitecture that might mitigate these physical limitations is being actively researched and developed.  Different materials such as graphene are being researched.  Different configurations are being considered, such as configuring in 3D instead of etching flat circuits onto the surface of a silicon wafer.  Whether or not a solution will be developed before physical circuit limitations are reached remains to be seen.


The useful lifespan of a PC, usually two to five years, is determined by Moore’s law.  This unavoidable trend is explained by the exponential rate at which transistor density doubles roughly every two to three years.  While the trend has slowed in recent years, it may continue to persist as new materials and microarchitecture are researched and developed.  For at least the next few decades, you can continue to expect any new PC to be obsolete within two to five years.  It’s just the way things are.