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My CPU temperature seems high.

How can I reduce it?

Can this cause problems?

What is a "normal" temperature?

By Tom Cumming


The faster and more powerful computers get, the more heat their components emit, and as the technology is progressing, this is becoming more and more of a problem. Most motherboards and processors today have a way of monitoring what temperature your processor and system are running at. This is normally accessed by looking in the BIOS setup. The BIOS setup is normally accessed by holding down a particular key when you first turn on or reboot your computer. On the screen it will normally tell you which key this is when you first turn on the computer, by a line like "Press Del to enter Setup". Refer to your motherboard manual for which key it is. You can also get at this information in your operating system if you have a suitable utility. The motherboard chipset manufacturers (Intel, VIA, AMD, etc) normally provide these as free downloads on their websites. However, AMD systems particularly are notorious for the temperature reading to be imprecise - they normally give the tolerance as ±15ºC, so the temperature readings should not be taken "without a pinch of salt".

Note also that CPU temperatures do vary: if you take a reading after your PC has been sat in standby mode for the last 10 minutes doing nothing, it will be a lot lower than if you take a reading immediately after playing Quake 3! The reading will also vary depending on the room temperature.

Different processor types can "cope" with different temperatures. It is a good idea to refer to your processor manufacturer's website or to find the technical specifications for your individual processor, and its "ideal" working temperature. Or another good site for this kind of information is

So, you now should know what your CPU temperature is, and what your CPU temperature "should" be. So what do you make of this?

If your CPU temperature seems high, compared with what you read on the specifications, you should take action. You should also realise that the maximum temperature given by the processor manufacturer is for a room temperature of 40 degrees celcius - normally the maximum designed operating temperature. So, if your room temperature is nearer 20 degrees celcius like most, then you should aim to get your processor temperature when under load to around 20 degrees celcius less than the manufacturer's quoted maximum figure. If a processor runs hotter than it is designed to, you run the risk that it will self-destruct. AMD processors are particularly good at this: if Intel processors overheat they are usually pretty good at switching off very quickly and surviving the ordeal, whereas AMD ones seem more likely to end up "fried".

Or, if your CPU temperature seems to be OK, but you are experiencing one of the following problems:

- The computer spontaneously switches off or restarts;
- The computer seems unstable: frequent "blue-screen" error messages;

this could also be due to an overheating CPU.

So, what can you do to avoid an overheating CPU?

1) The most important thing of all is the processor's heatsink and fan. The heatsink is basically a lump of metal with fins on it, to conduct the heat away from the processor. This is clipped onto the top of the processor. Then on the top of the heatsink is a fan that blows the hot air away.

The heatsink and fan must be suitable for the processor they are attached to. As well as fitting them physically, some are only certified to go upto certain processor speeds. If you bought the computer off-the-shelf from a reputable dealer, it should be safe to assume that the heatsink and fan selected are suitable for the processor. However if you have built the computer yourself, or upgraded the processor from the original, this might be an issue. If the heatsink and fan get clogged up with dust then they will not work as efficiently. It is a good idea to clean out the CPU fan of dust with a cloth every year or so, of course being very careful not to damage anything else inside the computer. Also make sure it is very firmly attached to the processor and not just sitting or dangling.

When chosing a CPU fan, do not be drawn into thinking that the higher the RPM (fan speed) the better. The size of the fan, the number of fins it has, the size of the heatsink, and it's surface area also have an impact, so do not rely on this solely. Get recommendations from people you know or from websites. The only thing that a high RPM guarantees is a lot of noise. The same goes for the CFM number - the amount of air moved - a high value does not necessarily mean a good heatsink. Sadly these figures are just included by manufacturers to make the product sound good to people that do not know what the figures mean. The only statistic worth looking at with heatsinks is the change in degrees celcius of temperature per Watt of power. The lower the number, the more effective the heatsink is. However, as most manufacturers do not quote this, just the mere prescence of this figure on a heatsink packaging makes it a lot better than a large proportion of the market!

2) Probably the next most important thing is the way the heatsink is attached to the processor. You may find that attaching your heatsink "bare" to the processor is not very effective, because either the processor or heatsink is not perfectly flat and not making contact all over. Therefore, it is normally better to use some kind of thermal transfer substance between the heatsink and the processor. However, there are different types: the "pad" type ones that most PC manufacturers use are nice and clean (which is why they are used in mass production) but are not as effective as the runny, messy ones you can buy from PC shops. It usually has the appearance of a sort-of cross between toothpaste and bicycle grease. This should be smeared thinly across the whole surface of the back of the heatsink. If you replace a "pad" compound with the messy stuff you should find your CPU temperature drop quite considerably: 5, 10 or even 15ºC. Only use a very thin layer of compound: remember it is only to fill the gaps where the heatsink is not touching the processor, to conduct heat from the processor to the heatsink.

3) Location of the system case: make sure your system case has plenty of room around it for air to go in and out, especially where all the vents are.

4) Other fans. If you find a CPU fan is not sufficient on its own, there are a number of other fans you can add to a system.

- Case fans. These improve airflow through the system case. Most system cases will have grills for one or two of these in the case. When fitting these you must be careful that they blow in the right direction to give a blow-through. If you fit a fan on the same side of the case as your power supply unit, make sure it is blowing in the *same* direction as the fan in the power supply unit (normally outwards), and if you fit a fan on the opposite side of the case to the power supply unit, it should be blowing in the opposite direction to the fan in the power supply unit. Again, is a good site to refer to for diagrams and more details on this. Make sure the grills in the case are kept free of dust as well. If you are short of case fan grills on your case, or they are only small ones, then consider changing your case, as you can add extra internal fans until you are blue in the face, but if the air inside it is only being circulated inside and not being replenished then it will not make a huge difference.

- Fans on hard drives. If you have a very fast hard drive that gives off a lot of heat, you can get fans that sit in a 5.25" drive bay and pump all the heat out the front it. They make good footwarmers in the winter as well. :-)

- Fans on graphics cards. Again, if you have a graphics card that gets very hot in operation, you can attach a fan to the heatsink to keep it cool.

- Expansion card fans. These are little fans that occupy a blanking plate at the back of the PC's case, to cool a PCI or ISA expansion card if you have any that get hot in operation.

Again, these fans must be kept clean to make them work best. Of course you will not need all of these different types of fans, or your PC will sound like a vaccuum cleaner. You will need to decide for yourself which of your PC's components are giving off the most heat to work out which will be most helpful for you. If you are concerned about the amount of noise that all this cooling produces, then a useful site to look at is . They sell a range of PC fans and other cooling devices, that are designed to be quiet in operation, and some other products to reduce PC noise.

5) Software. When the processor is not in use it can be made to go into a "standby" state to reduce heat. This does have a small performance hit though, but it means your CPU's idling temperature will be greatly reduced. It will not affect the temperature when hard at work, however. For AMD systems the best utility I have come across for this is VCool for Windows or LVCool for Linux. Unfortunately it does not appear to be being updated any more, so it will probably only work for older AMD systems.

6) Improve airflow around the case. This is done by reducing the amount of "clutter" inside your case to keep it as clear as possible. Keep all trailing wires neat and tidy. You can also gain a subtle improvement by replacing the ribbon cables that are used with storage devices, with equivilant round ones.

Copyright © 2001-2006 © Copyright Karl Davis.

No part of this site may be reproduced in any format.All documents author acknowledged are copyright retained by the author.

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