Back in the ancient times of personal computingthe mid-1980sone size fit all. For that matter, one color fit all. But thankfully, the computer industry has shaken things up a bit, allowing people to choose their perfect PCs' sizes, shapes, processor speeds, and memory types.
Many PC manufacturers have moved beyond the traditional tower and desktop sizes. Towers typically come in full, midsize, and mini, but micro and compact towers are out there, too.
Although the various styles appear to change only case sizes, motherboards also come in different sizes to fit in smaller cases. As the space gets tighter, airflow and cooling become more important, necessitating such changes as moving add-in card slots away from the CPU or installing motherboards that allow unobstructed air flow across the CPU.
Click here for a comparison of case sizes.
Let's Get Small
Rarely seen in consumer models, the full-tower is typically used for servers or workstations, in which there is a need for many drives and slots. At 21 to 26 inches tall and positioned vertically, it's the largest tower available and accommodates up to four 5.25-inch and ten 3.5-inch drives, with extra room for sound card panels, front-bay port adapters, and more. An AT motherboard typically powers these towers, letting you add as many as five PCI slots and even some old ISA slots.
The midtower is smaller than a full tower but still has enough room for expansion. At 17 inches tall or so, it fits about four 5.25-inch bays and four or five 3.5-inch bays. This chassis usually houses an ATX.
The mini-tower15 to 19 inches tall (or wide)is a common form factor for business and consumer desktops. It's large enough to allow expansion but will still fit on or under most desks. A typical mini-tower fits about two 5.25-inch and four 3.5-inch bays, which is enough room for most drive needs. The motherboard here is typically a Baby AT or the newer ATX.
Smaller still are micro-towers. At 13 to 15 inches tall, this form factor limits expansion greatly, but if all you need are two hard drives and two optical drives, this is a very practical size. Its small footprint lets it fit in small spaces and on top of desks. As expected, smaller cases need smaller motherboards. A Mini ATX or Flex ATX are usually found here.
Slimline desktops, or small form factor (SFF) desktops, are popular sizes for business use. They are horizontal units about 3 to 5 inches high. Components are typically packed in with little, if any, expansion room left. This makes sense for businesses, as many do not upgrade or expand their systems. The NLX is the motherboard of choice in these cases, since it has a small footprint and uses a riser card for slot expansion.
New Shapes and Sizes
A new and growing form factor is the compact case. Like other small, square boxes built specifically for multimedia PC that sit next to TVs, compact cases are generally single-purpose. They are typically smaller than a toaster and can even fit in your hand.
Some are meant for gamers, since they are easy to carry to LAN parties and can use the newest, fastest graphics card. Others are intended for corporate use as a single system shared by two employees. This lightweight form factor offers just enough space for large-capacity drives and the fastest graphics cards, as well as good air flow. A Baby ATX or a Micro ATX are the motherboards commonly found in these systems.
There's more to form factors than just case size. The all-in-one form factorpart of Apple's lineup since the first Macintosh systemshas long been popular with Mac users and is gaining popularity among PC users. An all-in-one is generally a feature-rich PC with the monitor (CRT or LCD), motherboard, CPU, and usually the drives rolled into one unit. PC manufacturers such as Gateway, MPC, and Sony offer all-in-one models.
For those who build their own systems, components are more important than chassis size. But for the rest of us, space can often be a deciding factor when choosing a desktop PC.