What is CPU Kernel Temp? How Hot Can a CPU Get?

CPUs are H-O-T


CPUs, also called Central Processing Units or Processors, are delicious little wafers made up of millions of electrical transistors and a little bit of silicon. Electricity produces a lot of heat, so when you’re talking about millions of electrical components packed into a space about the size of a silver dollar, you’re talking about some serious heat production. It really is a technological miracle that the whole thing doesn’t just melt. It will, however, stop working if that massive amount of heat is not managed properly.

CPUs on the Rocks

The immense heat a CPU puts off is handled in a fairly rudimentary way. A piece of metal that transfers heat well, like aluminum or copper, is placed on top of the CPU. This is called a heat sink. Heat sinks are designed with tall ridges, essentially maximizing surface area. This draws the heat away from the CPU and disipates it over the surface of the heat sink. A fan is almost always used on top of the heat sink, pulling away the warm air and replacing it with cool. To ensure conduction between the CPU and the heat sink, thermal paste is used to create a seal. This is often made of a silver or zinc oxide compound, so it too is adept at conducting heat.

Low, Safe, and Unsafe CPU Temperatures

What are considered to be low, normal, or safe temperatures for a CPU can be quite surprising by the standards of our environement. The coldest CPU that I’ve witnessed personally ran at 25° C – about 77° F. That, though, is extremely uncommon. Common and safe CPU temperatures are typically in the range of 35° to 45° C, or 95°-113° F. While not advisable for long term, many people allow their cpu to run as high as 60°C (140° F). Most consider any higher than that to be an extremely dangerous temperature that could quickly burn out their CPU.

Monitoring the CPU Temperature

The vast majority of modern motherboards come with some kind of software to help you monitor your CPU temperatures. This tool is usually found on a utility disc acompanying the board, or can often be downloaded from the manufacturers website. If you can’t find it from the manufacturer, a piece of software such as SpeedFan can be used to determine the temperature. All motherboards have built in thermostats these days, and are hard programmed to shut down should temperatures exceed a set limit. Some utilities allow you to set this limit yourself, while others may not.

Solving Temperature Problems


If you are experiencing higher than normal temperatures on your CPU, there could be several contributing factors.

Poor air flow: It is important that air constantly be flowing through your computer. Adding case fans, on to bring in air and another to push it out, can drastically help temperatures.

Old thermal paste: Over the course of several years, it is possible for thermal paste to break down and become less effective. Or, it could be that it wasn’t applied well originally. All you need to do to resolve this problem is remove the CPU fan and heat sink assembly, wipe off the old paste with a cloth or cotton swab moistend in rubbing alcohol, remove any lint, and apply new paste to the assembly, ensuring that you spread it evenly across the entire are the CPU will be in contact with.

Excess Dust: Dust is the number one killer of computers. It will get into the fan and heat sink causeing the fan to seize up or run slow, and the heat sink to clog as its essential heat dispersing surface area grows a dusty, insulative blanket. Keeping your computer clean using an anti-static vacuum or compressed air is critical to good performance, and will solve associated heat problems.