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Pentium 4 processors have a feature called Thermal Throttling which protects the CPU from overheating, preventing it from burning. Case the processor reaches a “trigger” temperature (which varies acordingly to the CPU model), the processor automatically lowers its speed, in order to make the generated heat to decrease. In the event of an overheating condition, your PC will be slower, but on the other hand your processor won’t burn. If even lowering the processor speed the temperature doesn’t drop to a safe level, the computer is turned off, in order to protect your CPU.

Actually there are two types of Thermal Throttling:

• TM1: Available in Pentium 4, Xeon, Celeron (Northwood and Prescott cores only) and Pentium M processors. In this type the Thermal Throttling function does not physically lower the CPU clock, but it inserts idle cycles between the instructions sent to the CPU core (i.e., it inserts wait states inside the processor), which lowers the processor performance, hence its temperature.
• TM2: Used on socket LGA775 Pentium 4 and Celeron and Pentium M processors, this type really lowers the CPU clock. This is done by lowering the CPU clock multiplier.

Average users won’t know if the Thermal Throttling is activated or not in their computers. If this feature is activated in your PC, it will run slower and also this means that you have an overheating problem in your computer, which has to be solved.

There is a very small program called Throttle Watch (https://www.panopsys.com) that can tell you if the Thermal Throttling is being activated or not. Just uncompress and run the program and you will see two windows. The top window shows how much the processor is being used. You can access a similar windows by pressing the Control Alt Del keys at the same time on Windows XP and then selecting the Performance tab.

But it is on the lower window that you will find the advantage of this program. This window shows if the Thermal Throttling feature is being used or not, and how much.

Figure 1: Throttle Watch.

[nextpage title=”Checking if Your CPU is Overheating”]

The best way to check if the protection feature of your processor is being used or not is to run a program that puts your CPU running at 100% of its capacity. One program that does that is BurnIn Test (https://www.passmark.com/ftp/bitstd.exe). Install and run it. In Configuration, Duty Cicles, leave checked only the CPU Math and CPU MMX boxes, raising from 50 to 100 the value present on these two options. This will make your CPU to run at 100% of its capacity while running this program.

Before starting testing your PC with BurnIn, configure Throttle Watch to save a data recording file on your desktop. Go to Settings, Journal File and configure Desktop and then press the F5 key while inside the Throttle Watch program. This will start recording the gathered data in a file called journal.txt on your desktop. Keep Thottle Watch open.

Start the BurnIn program clicking on the green light button and run it for the time you think it is enough (we suggest that you run it for at least 15 minutes). After finishing running this software (just click on Stop to finish it), go back again to Throttle Watch and press the F5 key again to stop the data recording. Open the journal.txt file and you will see if the Thermal Throttling was activated or not during the stress test.

Under normal condition, the “Throt” collumn has to be always showing zero. If it happens to be a number different from zero there, this means that the Thermal Throttling feature was activate and your processor has overheating problems.

If this is your case, you will have to check your CPU cooler installation. With the PC turned off, remove the CPU cooler, clean its base and also the processor surface with a cloth, apply a thin layer of thermal paste on the processor surface and reinstall its cooler. Repeat the test to check if the problem was solved. If it wasn’t solved, you will need to change your CPU cooler for another one with greater cooling performance than the one currently used in your computer.