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What Happens When a Computer Processor Runs at 100%?

written by: Percila Jackson•edited by: Simon Hill•updated: 9/10/2011

Get the lowdown on how to wrest control of your PC back from whatever is controlling it. Learn how to disable troublesome applications, and find out why your CPU runs at maximum capacity at times.

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    Processor at 100%

    A busy processor spiking to 100% utilization isn’t anything to be concerned about. Staying at 100% is something else entirely. This points to either a system that is being asked to do too much or a software glitch that is sending the processor into a loop or a virus.

    CPU Fan Activities like video encoding, bit torrent, CD/DVD burning, and gaming, all take up processor time and can in some circumstances send it to full utilization. This should happen rarely and only when the machine is doing a lot of work. The utilization itself isn’t the real issue here. It may prevent you from doing other things on the PC while it's working, but that’s more of an inconvenience than a problem. The main enemy of a maxed out processor is heat.

    As the processor is supplied with voltage from a motherboard, it converts it into unstable energy to drive the processor. This conversion wastes some of that energy and radiates it in the form of heat. That’s why your PC gets warm; the CPU, graphics card GPU, power supply and hard drives all use the same process. The harder these components work, the more heat they produce.

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    Keeping Cool

    In order to combat the heat, the CPU, GPU and power supply unit (PSU) all have heat sinks and fans which help to keep the components cool enough to keep working. They have enough tolerance to cope with full use for a set period of time, but not permanently. Also, as the components age, their effectiveness degrades meaning their capacity to offload the heat from the source reduces.

    So rather than spending money on aftermarket cooling, the first thing to do is to check out what is causing the processor to work so hard. For that we need the trusty Task Manager. So either press Ctrl+Alt+Delete or right-click on the task bar to call it up. The Task Manager will show us what processes are running and exactly how much processor power they are using as a percentage of the whole. This is an ideal way of identifying greedy problem processes and finding out why your machine is running slowly.

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    Task Manager Processes

    Windows 7 Task Manager As you can see in the second image, the CPU Usage is listed at the bottom of the window. Selecting the Processes tab will give you more of an idea of what is going on. These columns can be sorted by clicking the column headers. Clicking on CPU will sort the list by the most demanding application. This is ideal if we want to learn what keeps sending the CPU to 100%.

    The process you want to always see at the top is the Windows Idle Process.This is an internal Windows program that keeps the processor running to enable energy saving technologies like Speedstep and to prevent the processor from locking out.

    Monitor the Task Manager for a little while and watch when it gets to 100%. Check the Processes column to see who the culprit is and check it out. If it’s something you recognize like a video player or torrent client then you know the PC is simply being overburdened.

    If it’s a different program, it may be worth ending the process to see if the problem goes away (just be careful not to end an important system process.You can always check what the process is first by searching for it online). Highlight the process and click the End Process box in the bottom right corner. If the CPU usage goes down then you know that the program was either doing too much, got caught in a loop or has coding issues. Restarting the program again and seeing what happens is the best way to determine the cause. If the problem reoccurs then it is a problem with the program or configuration on your system. If the problem doesn't reoccur, then it just got itself caught up and is working properly now.

    The last reason for high CPU utilization is a virus. These don’t always show up in Task Manager, so if nothing shows, run a virus scan on your machine. If you have the software, run a deep level scan on reboot to check the Windows system files before they’re loaded. Many anti-virus programs come with the option to create a boot disc which will enable it to run before Windows is loaded. This is the best way of making absolutely sure your system is clean.

    A processor running at 100% isn’t necessarily going to do any damage, but finding out the cause is a good precaution. If you want to know more about analyzing your system check out “How to Run Diagnostics on a Computer."