Small form factor PC

Small Form Factor (SFF) computer systems are smaller than traditional mini-towers. SFFs include cubes, book-sized PCs and miniature Home Theater PCs (HTPC). SFF originally referred to systems smaller than the Micro-ATX. The term SFF is used in contrast with terms for larger systems such as "mini-towers" and "desktops."

The acronym SFF originally stood for "Shuttle Form Factor," describing shoebox-sized personal computers with two expansion slots. The meaning of SFF evolved to include other, similar PC designs from brands such as AOpen and First International Computer, with the word "Small" replacing the word "Shuttle."

The phrase Small Form Factor does not refer to standard form factors, as the phrase computer form factor does. Computer form factors are established standards for the physical dimensions of computer system components (e.g., IBM PC compatible components) to ensure they are interchangeable regardless of the vendor or the generation of technology. Because SFFs such as mini-computers and home theater boxes use proprietary motherboards and other components without industry-standard dimensions, "form factor" is technically a misnomer.

Designed to minimize spatial volume, SFFs are usually measured in litres. The phrase "small form factor" does not include traditionally small computing systems such as embedded or mobile systems. However, "small form factor" lacks a normative definition and is consequently misappropriated as a buzzword due to its growing popularity. Manufacturers often provide self-serving definitions.

Motherboard form factor comparison

Uses

Because they are built around small motherboards, SFF computers can be far smaller than typical desktop computers. They are often used in space-limited areas where normal computers cannot be placed. SFF computers have also found a niche as home theater PCs, as well as for mobile applications such as LAN parties. Manufacturers also can design SFFs to emphasize the aesthetic and ergonomic benefits of a small system which, unlike a full-size tower case, can easily fit on top of a small desk.

Some SFF computers even include compact components designed for portable computers, such as notebook optical drives, notebook memory modules, notebook processors, and external AC adapters, rather than the internal power supply units found in full-size desktop computers.

Features

Small form factor computers are generally designed to support the same features as modern desktop computers, but in a smaller space. Most accept standard x86 microprocessors, standard DIMM memory modules, standard 3.5 inch hard disks, and standard 5.25 inch optical drives.

However, the small size of SFF cases may limit expansion options; many commercial offerings provide only one 3.5" drive bay and one or two 5.25" external bays. Standard CPU heatsinks don't always fit inside an SFF computer, so some manufacturers provide custom cooling systems. Though limited to one or two expansion cards, a few have the space for 3/4-length cards such as the GeForce GTX-295 Most SFF computers use highly integrated motherboards containing many on-board peripherals, reducing the need for expansion cards.

Even if labeled "SFF," cube-style cases that support full-sized (PS2 form factor) power supplies actually have a microATX form factor. True SFF systems use TFX or smaller power supplies, and some require a notebook-PC style external "power brick."

SFF Types

The many different types of SFFs are categorized loosely by their shape and size. The ones below are available as of 2008.

Cubic

Shoebox case

Many SFF computers have a cubic shape. Smaller models are typically sold as barebones units, including a case, motherboard, and power supply designed to fit together. The motherboard lies flat against the base of the case. Upgrade options may be limited by the non-standard motherboards, cramped interior space, and power and airflow concerns. The Apple Macintosh Cube, released in 2000, and the Shuttle XPC are good examples of this design. MSI and Asus produce similar designs.

AOpen Inc. produced a stackable S120 case, allowing the user to stack up to four components vertically or horizontally. These layers can be for add-on cards, optical drives, and hard drives, using either internal power supplies or external AC adapter power sources. After the S120, AOpen made more small form factor cases for systems with Micro ATX and Mini-ITX.

Mini

Apple's Mac Mini is similar in size to a Mini-ITX based PC.

Until recently, SFF cases were usually sold as barebones units (case, power supply, and motherboard) to system integraters and home-based builders. In 2005, Apple Inc. introduced its Mac Mini (volume of 1.4 L, excluding external power brick). Later in the same year, the first AOpen mini PC MP915 (renamed to XC mini in 2007 since “mini PC” could not be registered as a trademark), was announced. The size of the XC mini series PC — 165(W) × 50(H) × 165(D) mm — makes it one of the smallest desktop PC systems (1.3L volume). It was criticized for looking like the Apple MAC mini, but Apple has not taken action on this subject. In February 2007, AOpen redesigned the case of the mini PC MP945 series.

As of 2006, major OEM PC brands such as HP and Dell have begun to sell fully-assembled SFF systems. These are often described as bookshelf units since they resemble a miniature tower case small enough to fit on a bookshelf. The HP Slimline series and Dell C521 (volume 1.65 L) are good examples of this trend. The Maxdata Favorit 300XS is another mini computer.

The HP Slimline uses a non-standard motherboard that is very similar in size to Mini-ITX.

In addition to its industrial use, the extremely small Mini-ITX motherboard form factor has also been incorporated into SFF computers. These are often extremely compact, incorporating low-power components such as the VIA C3 processors. The Travla C134 is an example of this design; it is somewhat larger than the Mac mini (7×10×2" vs 6.5×6.5×2"), and barely bigger than a standard 5.25" optical drive.

Nettop

Main article: Nettop

As of 2007, several other companies have released other very small computers that besides a small size, focus on a low price, and extremely high power efficiency (typically 10 W or below in use). These devices are called nettops and include devices as Zonbu, fit-PC, Linutop, and A9Home. With the release of Intel ATOM CPU, AOpen also made Nettop systems: the uBox series with model LE200 and LE210. The uBox series equips a dual core Intel Atom 270/330 processor, single channel DDR-II 533/667 memory, Intel 945GC+ICH7 chipset, three S-ATA connectors and 5.1channel high definition audio output.

Home theatre boxes

Essentially a bookshelf-style case laying on its side, a miniature HTPC replicates the look of other smaller-than-rack-sized home theatre components such as a DVR or mini audio receiver. The front panel interface is emphasized, with the optical disc drive rotated relative to the case in order to maintain horizontal mounting, and more motherboard port connectors (such as for USB) are routed to the front panel.

Computer-on-module

A Computer-on-module (COM) is a complete computer built on a single circuit board. They are often used as embedded systems due to their small physical size and low power consumption. Gumstix is one example of a manufacturer of COMs.

See also

• Case modding
• SFF-SIG

External links

• Losias SFF Modding and Hardware Community
• Gumstix, Inc.