When it comes to your CPU, how hot is too hot?
Above a certain temperature your CPU can become permanently damaged, but that temperature depends somewhat on the CPU and also for how long it experiences the elevated temperature.
Luckily, it’s pretty rare that your CPU will ever be operating under these conditions.
In this guide, we’ll look at what constitutes an acceptable, safe operating temperature for your CPU in order to avoid any damage and we’ll cover signs of heat damage and tips on how to prevent it.
We’ll also look at how your computer protects itself from heat damage.
CPU Operating Temperature Zones
There are three distinct temperature regions that your CPU can operate in:
The Dangerous CPU Temperature Zone is defined by temperatures above about 95C. In this region, the CPU is too hot and has reached a point where the heat it is generating is self-destructive. Continued operation in this region will lead to serious and permanent damage. If your CPU reaches this region regularly, something is wrong. The good news is that most computers will not continue to operate in this region, since they will take protective action and shut down. This is called thermal shutdown, and we’ll talk more about that in the next section.
The Elevated CPU Temperature Zone sees temperatures reach a level where performance begins to suffer. Your computer may appear “sluggish” or slow to respond. Fans may be noisier than usual because they are working harder to cool the system. In some instances you may experience program freezes or even a crash. If you’re using a laptop, it may become too uncomfortably hot to keep on your lap.
Sometimes, performing CPU-intensive tasks like playing games, watching Blu-ray and DVDs, ripping and burning CDs, and sharing files can push your computer into this region. While these temperatures affect performance, they are not high enough to cause damage to your CPU. This region is defined by temperatures from about 80C-95C.
If you’re thinking about getting into overclocking, make sure your CPU can handle it before diving in.
The Normal CPU Temperature Zone features temperatures low enough that the CPU functions normally with no degradation in performance or other ill effects. When your computer is just “sitting there”, i.e. not doing anything except background tasks, it’s called “idling”. A normal idle temperature is typically somewhere around 50C. Once you start actively using the computer, the CPU temperature will rise. This is completely normal and healthy; temperatures all the way up to about 80C are generally nothing to worry about.
CPU Thermal Shutdown
When thermal shutdown happens, you’ll know it. Typically your computer will just abruptly turn off. Depending on your computer it’s also possible that in the moments before the shutdown you’ll be informed by a pop-up window or screen that your CPU temperature is too high and the computer will shut down.
Thermal shutdown is managed by your computer’s BIOS (Basic Input/Output System), which reads one or more sensors that measure the temperature of your CPU. When the BIOS determines that the CPU has reached a dangerous temperature, it initiates the thermal shutdown sequence.
If you’ve experienced a thermal shutdown, you should leave your computer off for 10 or 15 minutes so that it can cool down. Don’t be tempted to move your computer into an extremely cold environment (i.e the refrigerator or outdoors in winter) to accelerate the cooling process. This temperature shock can cause components on your motherboard to be stressed and sometimes even crack.
After your computer has cooled, boot it back up. If thermal shutdown continues to occur, something is wrong with your computer’s ability to keep the CPU cool. Below, we’ll discuss some typical causes of inadequate cooling.
Causes of Inadequate Cooling
There are a host of things that can cause your CPU to get hotter than it should. Here are the most common ones:
1. Non-functioning fans: When fans aren’t spinning, they aren’t cooling. Your CPU relies on functioning fans to move heat out of it and out of the case. If your computer ever sounds eerily quiet, you should open up your case and verify that all fans are working.
2. Dusty fans, vents, or heat sinks: If you’ve ever opened up a computer that’s been in service for 5 or 10 years without a cleaning, you’ve probably seen this. Over time fans, vents, and heat sinks become caked with an almost unimaginable amount of dust, which inhibits their ability to move hot air out of the computer. If you see this inside your machine, give every dusty surface a good cleaning. You can blow the dust off with compressed air, wipe it off with your fingers or a cloth, or a combination of both. Just make sure the power is off!
3. Cable clutter: If you have a rat’s nest of cables packed into your case, they can restrict air flow, leaving hot air trapped inside. Eliminate any extra or unnecessary cables and tie-wrap the ones that remain to create a tidy environment that moves air efficiently.
4. Heat sink mounted incorrectly: Your CPU’s heat sink probably mounts to it using either clips or screws. It is actually pretty easy to mount it incorrectly so that it’s not flush with the top of the CPU. The heat sink relies on good mechanical contact with the CPU in order to properly transfer heat out of it, so if it’s not mounted correctly your CPU can overheat quickly. Make sure that all clips or screws are thoroughly locked down and the entire heat sink is flat on the CPU.
5. Thermal paste problem: If your thermal paste is more than a few years old, there’s a chance it’s past its prime. As thermal paste ages its ability to transfer heat out of the CPU suffers. Even if the paste isn’t very old, it could have been applied improperly. Too little paste or, believe it or not, too much paste can actually inhibit thermal conductivity, causing your CPU to overheat. If you’ve eliminated every other possible culprit, try replacing the thermal paste. Just make sure you clean all of the old paste off before applying a fresh coat.
Signs & Symptoms of CPU Damage
While thermal shutdown should always protect your CPU from heat damage, bad things do happen. For instance, your thermal shutdown might have been disabled in the BIOS settings or it could have just failed to trigger due to a faulty temperature sensor or other problem. If you suspect that your CPU got too hot and may be damaged, there are a few signs to look for:
1. That Smell! If you’ve ever fried a resistor or other electronic component you’ll immediately recognize the unfortunate and unique aroma of burnt silicon. Open up your case and take a whiff. You might also smell burnt plastic. Either of these are signs of possible heat damage.
2. Visible Damage. Inspect your CPU and other components for signs of charring or melting. Discoloration on the motherboard around the CPU and other components is also a sign of heat damage; circuit boards typically start to discolor at about 100C.
3. BIOS Beeps. Many BIOS systems will check for CPU heat damage at boot and alert you of the damage with a specific sequence of beeps. Consult your motherboard documentation for details on what to listen for.
4. Listen for Fans. The CPU controls your fans. If you power up your computer and let it run for about 10 seconds, you should hear your fans start running. If a fan isn’t spinning and you know that it’s not defective, this could indicate damage to your CPU.
If you suspect your CPU is struggling, check out our full Guide to the Signs & Symptoms of a Dying CPU.
Preventing Heat Damage – Software to the Rescue
If you are concerned that your CPU might be running too hot, there are many software applications that can be used to monitor the temperature. Some of the most popular ones are Real Temp, Core Temp, HWMonitor, and NZXT’s CAM. These are all pretty basic and easy-to-use programs.
We actually have a full standalone guide comparing Real Temp and Core Temp, so check that out if you want to install something quick and easy.
For a more in-depth solution that provides more information and diagnostic capabilities, check out HWiNFO 64.
In addition to temperature monitoring software, programs like Prime95 or AIDA64 can “stress test” your CPU to see how hot it gets when it’s working its hardest. These programs typically ramp up your CPU to perform lots of calculations and other processor-intensive functions.
You’ll still need to use your temperature monitoring software while running the stress test to actually see the temperature. Ideally, you should run a stress test for 1 hour, but you’ll get a pretty good idea of the maximum temperature after about 10 or 15 minutes.
You should now be familiar with the different ranges of temperatures that a CPU can operate in, as well as what’s dangerous and what’s acceptable.
You shouldn’t typically have to worry about heat damage because thermal shutdown should protect your CPU.
If it keeps happening though, run through the checklist of possible causes that your system might be overheating.
If thermal shutdown fails to trigger and you’re worried about CPU damage, open the case and look for the signs as well as listening to what your BIOS tells you.
Finally, you can give yourself peace of mind by using temperature monitoring software and even stress testing your CPU.