My desktop has started overheating -- how hot is hot?

Question

I have a two year old desktop, some random quad core HP desktop.

It used to run very quietly, but in the past month, the fans start up anytime anything "serious" is being done -- compiles, playing video, etc.

Right now, speedfan and speccy report the cores are between 50C and 70C. Speedfan reports this as hot. (Nice flame icon.)

Well, the system does sit on my carpet, so two weeks ago, I took off the lid, and cough cough it was pretty filled with dust. I got out an air can, turned on a vacuum and carefully got out all the dust that I saw on

• the CPU fan
• the case fans
• any fan I saw (graphics board)
• and blew out all the dust I could from all the circuit boards.

And then I closed the case back up. It has definitely run cooler since then, but it still runs hot, and I hear high speed fan noise I never heard before.

How hot is too hot? At what temps do consumer grade CPUs die?

What should I be looking to do?

• Replace CPU fan? (It seems to work)
• Replace power supply fan?

Assuming the dust problem is gone, where should I be looking to determine why the machine is heating up?

Epilogue: After following the various pieces of advice given here, the system did run cooler, but it was still noticeably running louder (hotter) than just a few months prior. I ended up purchasing a new cpu heatsink and fan and during installation found the cooling grease from the original heatsink was just a dried, cracked layer, probably more of an insulator than heat transfer agent. With the new fan AND the new heatsink compound, the system ran much much cooler and the fan rarely turns on.

Answer 1

There are clear guides from the manufacturers on operating temperatures for the various components in your system. Identify the important ones like CPU, GPU, RAM and Motherboard using something like CPU-Z, then look up the acceptable operating temperature for each component using the manufacturers specifications.

The key thing here though is that you're saying that you've noticed fundamental changes in the way your computer behaves. That's never good and there's usually a root cause that you need to identify to solve this. You probably don't want to be satisfied until you've solved this, even if you're 'within temperature tolerances'.

I'd suggest giving the PC a more thorough cleanout by taking it out to the roadside and blasting it with pretty much the entire can of air, until the motherboard and components look nearly new. You'll want to get into the graphics cooling spaces, around the CPU, around fan bearings, any heatsinks, and any corners where dust accumulates. Ditch the vacuum though, because they produce a static field at the end of the vacuum hose that can fry integrated circuits. Also beware of turning the air can upside down unless it's marked 'invertible' (and the invertible type have way less 'juice', so just use a regular one and keep it upright).

Worst-case, replace the heat compound on the CPU heatsink by following any one of the internet guides on the subject. If you're other component temperatures (GPU, motherboard) are also high though, this probably isn't the root cause of your issue.

BTW any time you're running a PC on a carpet, your dust problem isn't going to go away. Try and elevate it onto a hard surface, and ensure there's sufficient space at the rear of the unit to allow vented hot air from the case to circulate out into the room. Put your hand behind the case after an hour or two and if it feels even slightly warmer than the rest of the room, there's not enough space.

Answer 2

1. You can try replacing the thermal paste between the CPU and heatsink.
2. The performance of a fan is often specified by a value called cubic feet per minute (CFM), which represents how quickly the fan can move air. Sum the CFM ratings of intake fans and exhaust fans. If these values aren't reasonably close, you might want to install new fans to ensure balanced airflow.
3. What is considered "hot" for a CPU depends on the type of CPU you're using. This information is often specified in your manual, but it can also be found online on sites like CPU-World. For video cards, the typical maximum temperature is around 105 °C; temperatures of more than 90 °C can be considered "hot". That number is often a lot lower for desktop CPUs as their temperatures are measured at the integrated heat spreader (T_case) rather than at the core itself (T_junction) as is typical of mobile processors and GPUs.