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[ The PC Guide | The PC Buyer's Guide | Designing and Specifying PC Systems and Components | Detailed Considerations and Tips for Specifying Particular Components ]

System Cases

Description: The system case, also sometimes called the enclosure or chassis, is the physical box in which the main PC components reside. It is usually made of a metal cage with plastic and metal panels surrounding it, and comes in a variety of shapes and sizes. The case usually gets very little attention since it doesn't seem at first glance to be very important, but that's not in fact true.

Tip: For lots of additional information on system cases, including more discussion of many of the technical details, criteria and features mentioned below, see the Reference Guide section on the system case.

Role and Subsystems: The system case is responsible primarily for providing the physical structure that supports the motherboard, storage devices and other components of the PC box. It also protects these parts from damage and prevents the escape of harmful radiation they generate. The system case plays a key role in the cooling, expandability and aesthetics of the PC. It is not really part of any of the major subsystems as I have defined them, but it interacts with all of them.

Related Components: The case must be form-factor-matched to the power supply and the motherboard. It is usually specified and purchased at the same time as the power supply, but the power supply is a separate component.

Key Compatibility Selection Criteria: To ensure compatibility with the power supply and the motherboard, you must ensure that the case is of the correct form factor. The most popular form factor today is ATX, including its variants such as mini-ATX and microATX. Some systems use the NLX or WTX form factors; older machines use the AT, LPX and Baby AT form factors. Note that a case may support more than one different power supply or motherboard form factor; be sure to find out what the case can handle. A case that can accept more than one form factor is of course more flexible and will support both older and newer motherboards and power supplies. On a new system the case is usually chosen to match the motherboard, but on an upgrade the motherboard may be chosen to fit the existing case.

Size is also an issue in some situations. While the form factor standard should be sufficient guarantee that a motherboard of the same form factor will fit in the case, it sometimes isn't. If you are planning to use a very large motherboard be sure it will fit in the case you are considering.

Performance and Capacity Selection Criteria: There are three primary aspects upon which you will differentiate different cases:

  • Style: Cases are available in either desktop or tower styles. The primary difference between the two styles is orientation: desktop cases are short and wide and are meant to go, well, on the desktop, while tower cases are tall and narrow and can go on the desktop or on the floor. Tower cases are usually available in a wider variety of sizes. This is largely a matter of personal choice, and matching to your furniture and space requirements.
  • Size: Larger cases provide more room for the components of the system, allowing for more expandability of the system. They also often produce a system that runs cooler, since components can be spread out. Many people find them easier to work in as well, since the components tend to be less cramped. On the converse, they also take up more room and cost more than smaller cases.
  • Drive Bays: Cases come with external drive bays for devices like floppy and optical drives, and internal bays for hard disk drives. Some have more bays than others, even if they are the same size.

Quality Selection Criteria: The actual construction of the system case is very important. Good cases are made of heavy-gauge steel and are professionally machined with smooth edges. Cheap cases are made of flimsy stamped aluminum that you can literally bend with your hands, and which may contain sharp edges that can cut. Better cases also have much better fit and finish than cheap ones. Note that it is very difficult to tell the quality of a system case without actually seeing it and touching it in person--they all look pretty good in two dimensions. :^) Most reviewers of cases also don't pay a lot of attention to the actual quality of the unit.

Another quality issue is the general appearance and aesthetics of the case. This is a very personal, subjective issue, but one that is important to many people.

Important Features: Here are some useful features often found in better system cases. Note that the LEDs and switches on cases are pretty much standardized at this point, so I am not mentioning these specifically here:

  • Removable Panels: Standard case design is a one-piece "U-shaped" cover that fits over the frame of the case. Many newer cases have replaced this single, large and sometimes cumbersome cover with a set of individual removable panels, which are much easier to handle.
  • Motherboard Trays and Drive Cages: Better cases have removable parts into which the motherboard and hard drives can be installed. These parts then snap into the case. This makes assembly and upgrading of the PC easier and faster.
  • "Screwless" Covers: Older cases used four, six or more small screws to hold the cover in place. Many newer ones use a "snap-fit" design instead, usually in combination with removable panels. Some are "mostly screwless", using one screw that can be loosened or tightened by hand without a screwdriver. Again, this is for convenience, to make opening and closing the case easier.
  • Auxiliary Cooling Fans and Vents: The power supply has the primary ventilation fan for the system case contained within it. Many cases, especially larger ones, include additional cooling fans to increase the air flow of the system. Some have extra vents and mounting locations, where you can add your own fans if you wish.

"Magic Numbers" To Watch For: Thankfully, the system case is one component where there aren't any true magic numbers. The closest that one comes to seeing this is in the number of drive bays quoted for a case. That's a fairly straightforward figure, but make sure you find out what sort of bays they are--not all are created equal.

Performance Impact: The system case has no direct impact on the performance of the PC. However, it has an important indirect impact because of its importance to overall system cooling. High-performance systems usually need more cooling, and more room in the case to allow for proper air circulation.

Retail, OEM and Gray Market Issues: These issues are not terribly relevant to system cases, since failures are very uncommon. Few people buy cases at retail so most are sold as OEM components. Make sure you inspect the case thoroughly and return it immediately to the vendor in the event of trouble.

Importance of Manufacturer: Less than for other components; cases don't often require support. Generics are often fine for cases if they are well-made, but watch out for el-cheapo included power supplies.

Typical Component Lifetime: Cases never really wear out, so that's a non-issue. Obsolescence is also not much of a problem, as case form factor standards change slowly. I personally have a machine that has been upgraded three times and is still using a case from a PC I bought in 1992. For a new system I would strongly advise sticking to one of the newer form factors such as ATX.

Warranty Issues: Being a structural component, there are no major warranty considerations. Initial inspection for quality and damage is usually sufficient.

Driver Support Issues: Not applicable.

Special Specification Considerations: Upgrading a case requires essentially ripping the entire machine apart and reassembling it. This is an unpleasant task, but one that is usually needed only if doing some other upgrade. Still, since cases are inexpensive anyway, it makes sense to spend a few extra dollars to get a machine that has some room for expansion in the future. Don't under-buy the case to save five or ten dollars; unless you are absolutely sure you'll never work on the system, you'll likely be sorry later on.

Next: Power Supplies

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