Small form factor (abbreviated: SFF[1]) is a term used for desktop computers and for some of their components, chassis and motherboard, to indicate that they are designed in accordance with one of several standardized form factors intended to minimize the volume and footprint of a desktop computer compared to the standard ATX form factor.
For comparison purposes, the size of an SFF case is usually measured in litres. SFFs are available in a variety of sizes and shapes, including shoeboxes, cubes, and book-sized PCs. Their smaller and often lighter construction has made them popular as home theater PCs and as gaming computers for attending LAN parties. Manufacturers also emphasize the aesthetic and ergonomic design of SFFs since users are more likely to place them on top of a desk or carry them around. Advancements in technology combined with a reduced size enables a powerful computer to be a smaller size.[2]
Small form factor designs do not include computing devices that have traditionally been small, such as embedded or mobile systems.[3] However, "small form factor" lacks a normative definition and is consequently open to interpretation and misuse. Manufacturers often provide definitions that serve the interests of their products.[4] According to marketing strategy, one manufacturer may decide to mark their product as "small form factor" while other manufacturers are using different marketing name (such as "Minitower", "Microtower" or "Desktop") for personal computers of similar or even smaller footprint.
Yes, early small-form-factor machines (let's just call 'em SFFs) had some issues. OK, a lot of issues. Designed for the gimpiest casual user, these mini-PCs didn't offer many options in the way of upgrades or power. The cases were often too small to fit a full-size videocard [...] Still, two very specific users saw the SFFs' potential. First, home theater enthusiasts realized that these pint-sized PCs made for ideal media center hubs, and second, LAN partygoers naturally glommed on to them for the portability factor. [...] we could see the SFF market gaining a lot more momentum. Until then, enjoy being the first on your block to squeeze a full-size tower's worth of top-level gear into a shoebox-size package.