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Computer Case Characteristics

Here are the important characteristics of cases.

Form factor

Form factor is the most important thing about a case, because it determines which motherboards and power supplies fit that case. Mainstream cases are available in ATX and microATX and Extended ATX form factors. ATX (sometimes called Full ATX) cases accept full-size ATX or smaller microATX motherboards and full-size ATX or smaller SFX power supplies. microATX (sometimes called ATX) cases accept only microATX motherboards. Some microATX cases accept either ATX or SFX power supplies; others accept only SFX power supplies. Extended ATX cases accept full ATX and oversize ATX motherboards and ATX power supplies, and are ordinarily used only for workstations and servers.


Cases are available in many styles, including low-profile desktop, standard desktop, micro-tower (for microATX boards), mini-tower, mid-tower, and full-tower. Low-profile cases are popular for mass-market and business-oriented PCs, but we see little purpose for them. They take up more desk space than towers, provide poor expandability, and are difficult to work on. Micro-tower cases take up very little desk space, but otherwise share the drawbacks of low-profile cases. Mini/ mid-tower styles the dividing line between them is nebulous are the most popular, because they consume little desktop space while providing good expandability. Full-tower cases take up no desk space at all, and are tall enough that optical drives are readily accessible. Their cavernous interiors make it very easy to work inside them, and they often provide better cooling than smaller cases. The drawbacks of full-tower cases are that they are more expensive (and heavier!) than other cases, sometimes significantly so, and that they may require using extension cables for keyboard, video, and/or mouse.

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Figure 15-1: Antec Aria SFF case (image courtesy of Antec)


TAC (Thermally-Advantaged Chassis) cases cope with the high temperatures of modern processors by exhausting CPU heat directly to the exterior rather than inside the case. To accomplish this, TAC cases use a shroud that covers the processor and CPU cooler and a duct that connects the shroud to the side panel of the case. Because the location of the processor is standardized on ATX-family motherboards and the TAC shroud and duct are adjustable, a TAC-compliant case can be used with nearly any motherboard, processor, and CPU cooler. Figure 15-2 shows the TAC-compliant Antec SLK2650BQE case, a popular mini-tower model, with the TAC vent visible on the left-side panel.

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Figure 15-2: Antec SLK2650BQE mini-tower case (image courtesy of Antec)

Figure 15-3 shows the TAC shroud and duct arrangement on the side panel of an Antec SLK2650BQE case. Like most TAC cases, this one uses a passive duct arrangement, depending on the CPU cooler fan to move air from the CPU cooler to the case exterior. But Antec makes provisions for mounting an optional supplemental fan between the side panel and duct to move more air.

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Figure 15-3: Detail of TAC shroud/duct on an Antec SLK2650BQE case (image courtesy of Antec)

Some cases are not technically TAC-compliant but are designed to accomplish the same goal. For example, the Antec Sonata II, shown in Figure 15-4, is not TAC-compliant. Instead, Antec designed this case with a chassis air duct, visible as the dark gray area at the left of the case, that enhances cooling of both the processor and the video card.

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Figure 15-4: Interior view of the Antec Sonata II mini-tower case (image courtesy of Antec)

Similarly, the Antec P180, shown in Figure 15-5, is not TAC-compliant, but is engineered to minimize noise and maximize cooling. The P180 reverses the usual arrangement, putting the power supply at the bottom of the case instead of at the top. The power supply is contained within its own air chamber to keep the heat produced by the power supply out of the main area of the case interior, and is cooled by a dedicated 120 mm fan. The motherboard and drive areas are cooled by two standard 120 mm fans (rear and top), with provision for adding a third 120 mm fan at the front and an 80 mm fan for the video card.

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Figure 15-5: Interior view of the Antec P180 tower case (image courtesy of Antec)

Drive bay arrangement

The number and arrangement of drive bays may be unimportant if the system is unlikely to be upgraded later. Even the smallest cases provide at least one 3.5" external bay for a floppy drive, one 5.25" external bay for an optical drive, and one 3.5" internal bay for a hard disk. For flexibility, we recommend buying a case that provides at least one 3.5" external bay, two 5.25" external bays, and three or more 3.5" internal bays.


Cases vary widely in how easy they are to work on. Some use thumb screws and pop-off panels that allow complete disassembly in seconds without tools, while disassembling others requires a screwdriver and more work. Similarly, some cases have removable motherboard trays or drive cages that make it easier to install and remove components. The flip side of easy access is that unless they are properly engineered, easy-access cases are often less rigid than traditional cases. Years ago we worked on a system that experienced seemingly random disk errors. We replaced the hard disk, cables, disk controller, power supply, and other components, but errors persisted. As it turned out, the user kept a stack of heavy reference books on top of the case. As she added and removed books, the case was flexing enough to torque the hard disk in its mounting, causing disk errors. Rigid cases prevent such problems. The other aspect of accessibility is sheer size. It's easier to work inside a large case than a smaller case simply because there's more room.

Provisions for supplemental cooling

For basic systems, the power supply fan and CPU cooler fan may suffice. More heavily loaded systems those with fast processors, multiple hard drives, a hot video card, and so on require supplemental fans. Some cases have little or no provision for adding fans, while others provide mounting positions for half a dozen or more fans. In addition to the number of fans, the size of fans the case is designed to accept is important. Larger fans move more air while spinning more slowly, which reduces noise level. Look for a case that has mounting positions for at least one 120 mm rear fan and one 120 mm front fan (or already has one or both of those installed). Provisions for additional fans are desirable.

Construction quality

Cases run the gamut in construction quality. Cheap cases have flimsy frames, thin sheet metal, holes that don't line up and razor-sharp burrs and edges that make them dangerous to work on. High-quality cases have rigid frames, heavy sheet metal, properly aligned holes, and all edges rolled or deburred.


PC cases have traditionally been made of thin sheet steel panels, with a rigid steel chassis to prevent flexing. Steel is inexpensive, durable, and strong, but it is also heavy. In the last few years, the popularity of LAN parties has increased, fueling a demand for lighter cases. A steel case light enough to be conveniently portable is insufficiently stiff, which has led case makers to produce aluminum cases for this specialty market. Although aluminum cases are indeed lighter than equivalent steel models, they are also more expensive. Unless saving a few pounds is a high priority, we recommend you avoid aluminum models. If weight is important, choose an aluminum LAN party case, such as the Antec Super LANBOY case, shown in Figure 15-6.

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Figure 15-6: Antec Super LANBOY LAN party case (image courtesy of Antec)

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