Each of the major motherboard layouts described in Chapter 2 requires a different case type, although a few cases are designed to support more than one motherboard form factor. The form factors you're most likely to encounter include
• AT and Baby AT The AT and Baby AT form factors were the most popular in desktop and tower designs through 1995. The AT motherboard form factor is larger than the Baby AT form factor, and requires a larger case. Cases capable of holding full AT motherboards tend to be mid-size or full towers or desktop designs. Cases that can hold full AT motherboards can also almost invariably support Baby AT motherboards. These motherboards can also be used in compact mini-tower cases. I don't recommend buying a new AT or Baby AT case today unless you already have a matching motherboard. In this case, because the AT and Baby AT designs are now obsolete, I recommend you locate a case that can handle either AT or ATX motherboards, so that you don' t restrict your choices should you decide to upgrade the motherboard in the future. A
• ATX, Mini-ATX, Micro-ATX, and Flex-ATX As with the AT and Baby AT designs, E these four designs represent variants on the same layout, with each one in succession representing a smaller design. Because ATX motherboards are wider than they are deep, YO whereas Baby AT motherboards are deeper than they are wide, most ATX cases are desk- E
top, mid-tower, or full tower designs. Mini-tower ATX cases mount the power supply sideways, leaving space to the side of the power supply for the motherboard. This arrangement leaves little clearance for components on that side of the motherboard, typically including the CPU and memory modules. Mini-tower designs are more common for the smaller ATX variants. Full ATX cases can often accept smaller ATX variants, but not always.
• LPX LPX was the slimline case design common in the mid-1990s and earlier. Figure 4.3 shows an LPX computer. The details of LPX aren't perfectly standardized, so it can sometimes be difficult to match an LPX motherboard to an LPX case. I recommend avoiding such cases and their associated motherboards except under extraordinary circumstances, such as if you acquire a complete system at low cost.
• NLX NLX is LPX's replacement. Incorporating many of ATX's features, such as software-controlled power supplies, NLX is better standardized than is LPX, and is therefore a better choice than LPX for a new computer.
• WTX WTX is a new layout designed with Intel's new Itanium processor in mind. Unlike most earlier case designs, WTX includes specifications relating to required case features, case cooling, and so on. WTX cases are virtually non-existent in early 2000, but might become more popular after Itanium's release. You can learn more about WTX at http://www.wtx.org.
Once you've decided upon a form factor for your motherboard and case, you should consider some further factors to help make sure your case and motherboard match.
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