Why do CPUs get hot?

Why do CPUs get hot?
Cooling a CPU with moving air, using a heatsink and fan

In basic terms, a CPU is a collection of millions of microscopic electronic 'switches', all crammed into a tiny space known as its 'core'. Every time a single 'switch' operates, it generates a tiny amount of heat. Whenever the CPU is working inside your PC, millions of these switches are operating many thousands of times per second. The collective heat generated can be quite incredible, especially if the CPU is very busy.

To put this in real terms, consider a small room containing a single lit candle. It's not very likely that the single flame of the candle will noticeably warm up the room. Put a hundred candles in the room and after a few hours, you might just be able to feel an increase in the room temperature.

Consider now, cramming millions of candles into the room. It won't be very long at all before the temperature in the room becomes uncomfortably high.

To create faster CPU speeds, manufacturers need to add more and more 'switches' to the 'core' of the CPU, vastly increasing the quantity of heat generated by its operation.
Heat = Damage

Excessive heat, if unchecked, can cause all sorts of damage. Moderate overheating of the CPU can cause hidden damage and shorten its working life, while excessive overheating can actually cause the CPU to melt and destroy itself. With today's CPU's, this could all happen within a few seconds without some method of extracting the excess heat from the CPU core.
Help from Nature

So how can we get rid of the heat? A fundamental principle of heat provides the solution:

Heat always tries to move from hot things to cold (or cooler) things.

One 'thing' that is always in abundant supply and is easily heated in this way is Air. If we pass a flow of air over something hot, some of the heat will move to the cooler air as it passes over the hot surface. The larger the hot surface area, the more heat can pass into the surrounding air.

Because the core of our CPU is quite small, we need to spread the heat over a much larger surface area to help get rid of it effectively.

The Heatsink

Especially designed for the task, the Heatsink is placed directly on, and heated by, the CPU core. This offers a far greater surface area for the heat to move to the passing air.

Since the transfer of heat relies on complete contact between the CPU core and the heatsink base, Thermal Interface Material, a fine grease or thin pad, is usually applied in the join between the heatsink base and the CPU core to maximise the efficiency of heat transfer.

CPU Cooling

In the past, a heatsink alone was sufficient to keep a CPU cool, but as newer CPUs are increasingly generating large amounts of unwanted heat, the surrounding air becomes too hot and the heat transfer stops.

To keep the process going we need to continually replace the heated air surrounding the heatsink with cooler air. The most efficient way to do this is with a Fan.

The fan-assisted heatsink is now quite effective at transferring heat from the heatsink to the air, but must have a good supply of cooler air for maximum efficiency. Since the CPU is mounted inside the PC Case, the hot air needs to be removed and replaced with cooler air.

Heatsink and Fan Maintenance

In most cases, The PSU has a built-in fan, and is quite adept at removing the hot air from inside the case, but it can be advantageous to add an additional fan, nearby the CPU cooler, to push more hot air out of the back of the PC case.

As hot air is removed from the PC Case, cooler air is drawn from the outside of the PC Case, through the pre-cut vents in the side and front panels. It is for this reason, that it is imperative to maintain a good airflow around your PC when it is in use and not to block any of the vents or fan outlets. Again, additional fans in the case side (or front panel) can be used to force cooler air into the PC case.

An unfortunate side-effect of the use of Air in this system is Dust. Over a period of time, fan blades and heatsinks will become covered with a layer of dust, which gradually reduces the efficiency of the transfer of heat and the effective operation of the fans.

Regular checks on the heatsink and fans in your PC system and the removal of any build up of dust with an air-duster will keep the system in top condition and maximise the life of your CPU.

What is a PC?

What is a PC?
An overview of the basic building blocks of a Personal Computer

The PC is an extremely versatile tool that can assist us in both our personal and professional lives in a countless number of ways.

It's extreme adaptability is, in part, due to the nature of its construction. Over many years, PC electronics industries have strived to agree on certain 'standards', enabling them to develop a wide range of devices and applications that are 'PC compatible' - that is, that can be fitted / connected / installed to a PC with the minimum of effort.

Throughout this section, we will study the key components you will need to build a basic PC.


To help you decide what to buy, check the product brochures of the leading PC suppliers and also do a search for some hardware reviews on the Internet. These will give you an idea of what is available and what would be considered a 'reasonable' specification PC.

There would be little point in building your own PC cheaply, for example using an old processor and motherboard, and then finding that it was very slow or even incapable of meeting your requirements.

Once these components are completely assembled and connected correctly, you have created what is fundamentally a PC.

What is Transcription

Transcription is the conversion into written, typewritten or printed form, of a spoken language source, such as the proceedings of a court hearing. It can also mean the conversion of a written source into another medium, such as scanning books and making digital versions. A transcriber is a person who performs transcriptions.

In a strict linguistic sense, transcription is the process of matching the sounds of human speech to special written symbols using a set of exact rules, so that these sounds can be reproduced later.

Transcription as a mapping from sound to script must be distinguished from transliteration, which creates a mapping from one script to another that is designed to match the original script as directly as possible.

Standard transcription schemes for linguistic purposes include the International Phonetic Alphabet (IPA), and its ASCII equivalent, SAMPA. See also phonetic transcription

Transcription is often confused with transliteration, due to a common journalistic practice of mixing elements of both in rendering foreign names. The resulting practical transcription is a hybrid called both transcription and transliteration by general public.

In this table IPA is an example of phonetic transcription of the name of the former Russian president known in English as Boris Yeltsin, followed by accepted hybrid forms in various languages. Note that 'Boris' is a transliteration rather than transcription in strict sense.

The same words are likely to be transcribed differently under different systems. For example, the Mandarin Chinese name for the capital of the People's Republic of China is Beijing in the commonly-used contemporary system Hanyu Pinyin, and in the historically significant Wade Giles system, it is written Pei-Ching.

Practical transcription can be done into a non-alphabetic language too. For example, in a Hong Kong Newspaper, George Bush's name is transliterated into two Chinese characters that sounds like "Bou-sū" (布殊) by using the characters that mean "cloth" and "special". Similarly, many words from English and other Western European languages are borrowed in Japanese and are transcribed using Katakana, one of the Japanese syllabaries.

After transcribing

After transcribing a word from one language to the script of another language:
one or both languages may develop further. The original correspondence between the sounds of the two languages may change, and so the pronunciation of the transcribed word develops in a different direction than the original pronunciation.
the transcribed word may be adopted as a loan word in another language with the same script. This often leads to a different pronunciation and spelling than a direct transcription.

This is especially evident for Greek loan words and proper names. Greek words are normally first transcribed to Latin (according to their old pronunciations), and then loaned into other languages, and finally the loan word has developed according to the rules of the goal language. For example, Aristotle is the currently used English form of the name of the philosopher whose name in Greek is spelled ̓Aριστoτέλης (Aristotélēs), which was transcribed to Latin Aristóteles, from where it was loaned into other languages and followed their linguistic development.(In "classical" Greek of Aristotle's time, lower-case letters were not used, and the name was spelled ΑΡΙΣΤΟΤΕΛΗΣ.)

Pliocene comes from the Greek words πλεîον (pleîon, "more") and καινóς (kainós, "new"), which were first transcribed (latinised) to plion and caenus and then loaned into other languages. The historising latinisation of <κ> by refers to the times where Latin pronounced as [k] in all contexts.

When this process continues over several languages, it may fail miserably in conveying the original pronunciation. One ancient example is the Sanskrit word dhyāna which transcribed into the Chinese word Ch'an through Buddhist scriptures. Ch'an (禪 Zen Buddhism) was transcribed from Japanese (ゼン zen) to Zen in English. dhyāna to Zen is quite a change.

Another complex problem is the subsequent change in "preferred" transcription. For instance, the word describing a philosophy or religion in China was popularized in English as Tao and given the termination -ism to produce an English word Taoism. That transcription reflects the Wade-Giles system. More recent Pinyin transliterations produce Dao and Daoism.