Is the performance of a CPU affected as it ages? [closed]

Is the performance of a CPU affected as it ages?
after a year of intensive use, the circuits degrade and fewer electrons can pass since the pathway is narrower, etc.

No,

Crystal oscillator

the speed of a CPU is determined by a crystal oscillator - so far as I know this is an external part for most CPUs

Picture from TechRepublic article

Crystals undergo slow gradual change of frequency with time, known as aging.

However, I suspect this is not a significant factor.

Drift with age is typically 4 ppm for the first year and 2 ppm per year for the life of the DT-26 crystal.

(from TI concerning an RTC IC but I believe this rate is similar for timing crystals in general)

CPU Semiconductor changes

Breakthrough posted a link to an IEEE article that describes the myriad of ways that semiconductors are affected over time.

It is possible therefore that the maximum clock speed the CPU is capable of will decrease over time. However in most cases this will not cause the CPU's theoretical maximum possible speed to fall, within a year, below the actual operating speed set by the crystal oscillator. Therefore a CPU that has been stored for a year will run at the same speed as an originally identical CPU that has been used continuously for a year.

CPU Thermal regulation

Many CPUs reduce their speed if their temperature exceeds a pre-set threshold. The main factors that might cause a one-year-old CPU to overheat are not to do with semiconductor degradation within the CPU itself. Therefore these factors have no bearing on the question as formulated.

It is unlikely that a given pair of identical CPUs will diverge in capability within one year sufficiently to trigger thermal issues that require one of them to run itself at a reduced speed. At least, I know of no evidence that this has occurred within one year on a device that is not considered a warranty failure due to manufacturing defect.

CPU Energy efficiency

Many computers, especally portable ones, are similarly designed to reduce energy consumption when idle. Again this is not really relevant to the question as stated.

In theory, no, a CPU should run at basically the same speed its entire life.

In practice, yes, CPUs get slower over time because of dust build-up on the heatsink, and because the lower-quality thermal paste that prebuilt computers are often shipped with will degrade or evaporate. These effects cause the CPU to overheat, at which point it will throttle its speed to prevent damage.

Cleaning the heatsink and reapplying the thermal paste should make it as good as new, though.

Note: if you're asking this due to having an old computer slow down, there are other reasons (usually dying hard-drives or popped capacitors) that old computers will slow down over time.

Short answer, no a CPU will not get slower with age.

Slightly longer answer:

A CPU will work so long as all of the connections and transistors are working properly. While in a normal wire there might be movement that can make the connection intermittent, that is not the case on the CPU as:

• the circuits are etched into the silicon
• things are much smaller

If something does break, anything can happen: from bad math to the computer not starting up.

I would argue - that the essential heart of this matter - has far less to do with physical hardware - as it does with how our perceptions - and the relative performance of the software that we run - change over time.

In a world of 1's and 0's - there is very little that can happen, especially to the CPU - that would drastically (or even statistically) alter the machine's overall performance - other than a total failure.

This question caught my eye because I've recalled times in my life where I couldn't believe the machine I was using - was the same one that maybe only a few years before I thought was so fast - that I was now being tortured by what at that point seemed to be interminably slow.

On a brighter note - as Moore's lawyers have seemed to be on recess - software developers have made major improvements in recent years - that seem focus on fine-tuning performance vs. relying on brute power. It is no exaggeration when I say that my 8-Core Xenon 2.8 GHz Mac Pro seems 2X or 3X faster now than it did when purchased in 2008. These are meaningful and measurable differences that could only be due to massive improvements / optimizations on the software side.

What I'm saying is that the human mind / our perceptions / our expectations, combined with other more flexible aspects of the operating environment are exponentially more impactful than any variations from a factory spec - that you may be worried about.

If I purchase two identical CPUs, and use one long term (say one year), will it be identical in speed to the unused CPU?

Most likely, yes. The speed a CPU runs at is variable, and set by the end user (although usually set automatically as per the manufacturer's specifications). However, you might find that at the end of the first year, the unused CPU (assuming they were truly identical to begin with) overclocks better than the used CPU. This effect can be attributed to transistor aging, which you hinted at later in your question:

While a CPU has no moving parts (other than the external fan), it does have circuits that can be damaged by heat, and voltage spikes. Lets say that after a year of intensive use, the circuits degrade and fewer electrons can pass since the pathway is narrower, etc.

This is exactly the case, and is precisely what happens after a CPU is used.

Similar to a vehicle, there is some wear-and-tear on the conductors as electrons pass through them. Heat also affects the transistor aging, which is why the CPU die is designed for a particular range of operating temperatures. During operation, the electrons have to tunnel through some layers in the semiconductor materials, degrading them over time. This causes the switching speed of the individual transistors to increase over time, making them "slower".

However, as I said before, the CPU speed is set by the end user. It's a synchronous digital circuit, and will run as fast as you tell it to - even if the propogation delay exceeds the switching time, and the computer crashes. This is what will happen as a CPU ages. Over time, the various sub-units in the CPU will take longer and longer to finish their computations, leading to instability in the CPU.

This effect can be mitigated by slowing the clock speed down, making the CPU slower but compensating for the increased propagation delays. This effect can also be mitigated by increasing the CPU voltage (causing a reduced switching time for the transistors, allowing for a higher clock speed), but raising the CPU voltage will only cause the transistors to age faster.

This is why we say a processor gets slower as it ages - the processor becomes unstable at higher speeds, requiring you to lower the clock speed over time. The good news is that this effect is usually noticable on a timescale of years.