Maybe you’re out in the market looking to buy a used CPU, or perhaps you suspect your current one is overheating and want to find out. Here’s how to tell if a CPU may be damaged from past overheating.

1. Check the CPU Temperature

This is by far the best way to judge whether or not a CPU is overheating, and from that information, you’ll be able to judge more accurately whether or not it has been damaged. No, you won’t need a thermometer and a screwdriver.

Your CPU has built-in temperature sensors to monitor and regulate its own temperature as necessary. You’ll need to access the readings on these temperature sensors.

GPU temperatures can simply be checked through Task Manager. But CPU temperatures don’t show up there for whatever reason, so you’ll need to install some software. There are a variety of applications that allow you to check your CPU temperatures, each of them with its own unique set of features.

MSI Afterburner is a simple, all-in-one metric monitoring software that allows you to check your CPU temperatures in real time (and it can do a lot more). It’s also one of if not the most popular applications of its kind. While originally intended to be a GPU-overclocking software, it also allows you to view your CPU temperature, so it’s perfect for our purposes.

Another great option is Core Temp. It is a much smaller application with more limited functionality, but it will get the job done just as well if you’re all interested in CPU temperature monitoring.

Once you have either program installed, launch it and check your CPU temperatures while idle (when no applications are open) and while performing a demanding task, such as gaming or rendering.

While there’s no exact definition of what idle and under load constitute, a CPU operating under 10% utilization can be considered idle. By contrast, a CPU operating at over 70% can be considered under load.

You can see your real-time CPU utilization in the above apps. You can also see utilization in the Task Manager. Most CPUs will run at 86 to 104°F (30 to 40°C) when idle and 158 to 176°F (70 to 80°C) when under load. If it exceeds these temperature ranges, you may have an overheating problem.

Run a CPU Stress Test

A Prime95 stress test is running on a computer.

A stress test will make your CPU go the whole nine yards. In other words, it will cause it to run at 100% utilization.

You’ll rarely see such high utilization in your day-to-day computer usage, even while gaming, but stress testing a CPU helps identify heating/cooling problems.

You’ll need to install software for this, too. CPU-Z is a popular testing software. Another similar software is Furmark. You can go with either. Both will squeeze every last bit of juice out of it. Once installed, run a stress test. Your CPU should stabilize at its maximum temperature within a few minutes.

Temperatures up to 80°C (176°F) are fine. Any higher, and there is some cause for concern, especially if you have a newer CPU. Newer processors are more energy-efficient and have better cooling solutions, so they tend to stay cooler. A new processor breaking 80°C (176°F) indicates something is wrong within the system.

One last thing you may be wondering: if a stress test causes a CPU to reach its highest temperature, could it damage it by overheating it? The answer is no. A stress test only lasts a few minutes at most. Overheating usually leads to hardware damage when it remains unaddressed for long periods.

2. Examine the CPU Chip Directly

If you just checked your temperatures and weren’t too impressed, it may be worth inspecting the CPU chip directly. To do this, you will have to open up your PC and tinker with the internals, so it’s best to have previous experience.

If you aren’t confident in your abilities and are afraid of messing something up (that’s okay, I’ve been there), you should get the help of an expert or hire a professional. They’ll be able to identify and fix any problems with heat dissipation.

You probably already know what to do if you built your own PC. Open the PC casing, unscrew the fan, and you’ll uncover the CPU chip itself. Honestly, it’s not as difficult as it sounds.

Look for decoloration, both on the chip itself and its socket. Decoloration is a clear indicator of overheating. Also, check the thermal paste content on your CPU chip. Thermal paste is a highly conductive liquid that transfers heat from the chip to the fan’s heatsink.

It dries up over time, though, so it needs to be replaced every few years. If the thermal paste on your CPU has dried out, you may have the answer to why the chip is overheating. Remove the existing residue with a cotton swab doused in thermal paste remover and apply new thermal paste.

Once you’re done, reassemble the system. If dried-out thermal paste were the issue, your CPU temperatures would improve considerably. Still, the lack of thermal paste probably shortened the CPU’s lifespan. If you don’t see an improvement in temperatures, the problem may lie in the fan.

Check the airflow inside your case to ensure the CPU can do its job effectively. If the air inside the case is too warm, it can cause overheating for any component inside the system, irrespective of how good the cooler is for that part.

3. Check for High Fan Noise

A CPU cooler's fan is spinning up fast to keep the CPU cooler.

In both desktops and laptops, CPUs are typically cooled by a heatsink attached to a fan. The temperatures dictate the fan speed. So when a CPU heats up, the attached fan blows faster to cool it off.

The attached fan will operate at its top speed in an overheating CPU to increase cooling. CPU fans are relatively quiet compared to your GPU and power supply fans, but you’ll still hear a loud whirring noise.

No Fan Noise?

Say you’re doing something known to be demanding, such as running a CPU-intensive program, playing a game, or running complex code. You notice that the CPU fan doesn’t seem to be blowing any faster than it was previously, or maybe it doesn’t seem to be blowing at all.

That’s suspicious because any modern-day CPU under full load for longer than a few minutes will produce enough heat to cause its cooling fan to spin noticeably faster unless the local air temperature is near freezing. In this case, the fan may be faulty. Without a cooling solution, even the most power-efficient CPUs will be prone to overheating.

Nothing is drawing the heat away from the CPU other than the passive heat conduction to the heatsink. As the heatsink reaches the same temperature as the CPU, the heat dissipation rate will diminish until it’s so slow that it may not matter. A CPU that operates without a cooling fan will likely be damaged by overheating soon if it hasn’t already.

Another thing to check is that the CPU cooler is mounted properly to ensure proper contact between it and the CPU.

4. Judge Overall System Performance

A man is watching the performance of his PC while playing a game.

If your CPU is overheating, poor system performance is one of the first indicators you’ll see in your day-to-day computer use. The CPU is the brain of your computer. It issues all the commands, carries out all the calculations, and tells all the other components what and what not to do.

Unsurprisingly, a CPU damaged by overheating would lead to poor overall performance. You’ll notice a deterioration in load speed, and some processes might even fail to complete. Admittedly, this is only a general indicator of hardware health. Many other components in your PC could also be at fault.

Poor system performance can be attributed to various factors, but a failing CPU is one of the more likely culprits.

5. Watch Out for System Crashes

System crashes are, needless to say, quite frustrating. You launch a new application, and suddenly, the system stops responding entirely, requiring a restart to resume normal function. Software issues usually cause system crashes. You’ll know this is the case when a particular application causes your computer to shut down.

However, it’s also possible for an overheating CPU to cause a computer to crash. You see, CPUs have a built-in temperature limit. The manufacturer sets this limit and exists to prevent it from sustaining damage due to overheating. It’s usually just over 212°F or 100°C.

You can find the temperature limit for your particular processor on the manufacturer’s website. As a CPU nears its temperature limit, it will slow down to consume less power and generate less heat. This is called thermal throttling, and we’ll talk more about it shortly.

Most CPUs will, at this point, reach a stable temperature. However, if the CPU continues to heat up and reaches its temperature limit, it will shut down instantly.

This is a very common occurrence in laptops, where heat dissipation is very limited, to CPUs continue to heat up until they’re forced to shut down to save themselves from damage. Now, 212°F (100°C) is a pretty high temperature for a CPU. For reference, most run at a comfortable 158 to 176°F (70°C – 80°C) under full load.

To be honest, even 176°F (80°C) is pushing it, considering how effective modern thermal solutions are. The point is that before a CPU shuts down due to overheating, it will likely operate at 176 to 212°F (80 to 100°C) for some time, which will cause its lifespan to shorten somewhat.

When it shuts down, the CPU will sustain some internal damage from the rapid drop in temperature. If a CPU continues overheating and shuts down this way over the long term, it’s more likely to malfunction.

A faulty storage device can cause system crashes, so crashes alone aren’t conclusive evidence of an overheating GPU. They’re a solid indication, though.

6. Check for Lag and Stuttering in Games

Gaming is a very resource-intensive task. Most 3D triple-A titles today involve a ton of computation. Simply put, when you’re gaming (especially if it’s a newer game), your CPU is likely running very close to its maximum capacity.

Now, this is fine. There’s nothing wrong with running a CPU at full power as long as it stays at an acceptable temperature. Naturally, when a CPU runs at its full potential, it will consume a lot of wattage and convert all that power into heat.

A CPU that overheats will throttle, reducing its processing speed, power consumption, and, as a result, heat production. This will cause the running game to lag and stutter. Frame drops caused by the lack of CPU output are markedly worse than playing at a lower frame rate in the first place. The game will feel super jittery.

An easy way to tell that your CPU is overheating is to notice how the game performance changes over the next hour. If a game runs smoothly when you start playing, but the framerates drop, or you see lag spikes after a while, chances are your CPU is overheating.

A damaged CPU won’t work as efficiently, further exacerbating the problem.