Case (computer chassis)
A computer case (also known as a chassis or tower) is often viewed as simply an enclosure in which the hardware components of a PC are stored, but this is not entirely true. While visual considerations play a part in effectively choosing a computer case, its real functions are actually more varied, and are ultimately important to the overall functioning of the system. There are many types of case, differentiated by size or the materials used, and each one has its own place in the market. To understand the difference between cases, it is necessary to know how exactly the case affects the system.
Purpose of a Computer Case
Besides the obvious of housing all the hardware of a computer, one of the most important functions of a case is the cooling of the components. Simply having a fan or heatsink on the CPU or other components is not enough to ensure that a system functions at peak efficiency; once the fan extracts the heat from the component, it releases it into the case, from which it must be removed. Heat is the primary source of "ageing" for computer components, so if the heat builds up in the case, then it leads to shorter lifespans for each piece of equipment. For this reason, a case must provide enough ventilation and airflow from case fans so that the heat can be exhausted and keep the components cool.
Computer cases also provide protection - the components must be protected from static electricity, moisture, dust, and various other substances which could damage them. Finally, a case dulls the noise of the multiple fans often installed in most computers, so the noise isn't distracting when working near the computer.
Case Form Factors
There are several basic types of computer case, and the main difference between them is the type of motherboard they were built to accommodate (otherwise known as "form factor"). The most common form factor is ATX, which stands for Advanced Technology eXtended; this is defined mainly by its printed circuit board size (305mm by 244mm) but also by the layout of the motherboard. Most computer cases on the market today were built for ATX motherboards.
A more recent form factor is BTX, which was designed to replace the ATX standard. It has a larger PCB size (325mm by 266mm) and was initially designed to alleviate problems with power consumption and heat generation on the ATX motherboards. However, as the components themselves were redesigned to compensate for these issues, the BTX form factor was not widely adopted. BTX and ATX are not interchangeable, so ATX motherboards must be housed in an ATX case - this is partially due to size, and partially because the mounting holes for motherboard screws are in different places.
Types of Computer Cases
Leaving aside the issue of motherboard size, there are several different sizes for cases as well.
Mid towers are the cases with which most people would be familiar; PCs in workplaces and schools tend to be housed in this size of case. Mid tower cases are approximately eighteen inches high, with between two and four external bays (which can be used to use DVD, CD and Blu-Ray drives).
Full towers are much larger, typically around 22 inches high, and can have anywhere up to sixteen drive bays - these tend to have much better cooling ability than smaller cases, and allow the installation of high-end components which are generally quite large. Full towers are enthusiast cases, highly popular among the overclocking crowd, which have lots of room for cable management (hiding the cable bundles from the power supply to the components, which otherwise hang down in the middle of the case impeding airflow). Along with server cases, full tower cases tend to be geared towards easy upgrading and maintenance and are therefore large, accessible, and have lots of room for expansion.
Smaller options include minitower cases, which have space for only one or two bays, and are generally between thirteen and sixteen inches tall. These are some of the least imposing cases, though their small size makes maintenance more difficult and their cooling performance is usually a secondary consideration to their size.
HTPC (home theatre PC) cases, which house only the components needed to make a personal computer along with the ability to view and record music, video, and photos, are typically very compact so they so they can fit in a TV stand or home theatre setup. The components needed to run a PC of this type are not large - not all HTPCs are fully functional PCs, and generally they just allow the combination of all of a room's media devices into one place.
The materials from which a case is made are also an important consideration. Steel, plastic and aluminium are the most common materials, and each has its own advantages and disadvantages. All steel cases are generally extremely heavy, have decent cooling and fairly priced. Computer cases built with large amounts of plastic are both cheap and lighter in weight than all steel cases, but their cooling performance tends to be sub-par; indeed, the plastic used for these cases can be adversely affected by the heat from the components. Aluminium is becoming more popular with case manufacturers, primarily because it is relatively inexpensive yet durable and lightweight. Aluminium also provides superior cooling performance, especially when compared to plastic. Unfortunately, aluminium cases usually come with a premium price tag compared to all other case materials.
Ultimately, there are many different reasons for wanting to build a computer. Whether it's to have a gaming computer on which to play the latest games, or a small, functional computer on which to do spreadsheets or word documents, choosing the correct case is an integral part of building a PC. Hopefully, these facts will have sufficiently explained why there is such a variety of cases on the market, and why familiarising oneself with the options is extremely important.
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