The home has been gradually becoming a media-centric entity with many heterogeneous application and services. At the same time, consumers are adopting new technologies for their multimedia entertainment, music, videos, and more. This trend requires increasing needs for storage solution for digital media and automation programs. Most home users use a combination of desktop PC with their respective home devices. Nevertheless, these devices are already overwhelmed by the volume of services flowing into their home.

To accommodate the growth of services in homes, integration and configuration of home technologies must be able to facilitate customizability and extensibility. Unlike industrial application, typically configured by skilled professionals, home systems interface and program should be understandable by home users. This will ensure easy integration and scalability for more services that is desired by home users. Often, dedicated services for home systems are either deployed or associated with user’s desktop PC. An example application is the media server for home entertainment. Although desktop PCs continue to grow in terms of performance with better clock speeds, multiple cores of processors, gigabytes of memories, it is important to highlight that most of the mentioned resources are optimized by user interfaces, operating systems and graphics together with video-intensive applications. Availability of high performance processors leaves in their wake slower units with low power requirements called as small form factor systems. Small form factors refer to new class of smaller sized computer and have all the identical features of a desktop PC. Small form factors are low priced and have achieved a level of performance that is more than required for wide range of applications. Applications for small form factor systems include data loggers, test equipment, robotics, industrial control and home systems. Originally intended for industrial solutions, small form factors are now slowly making their way into home scene as more multimedia services are changing the nature of home systems in managing digital contents.

Why Small Form Factors

In recent times, there is gradual transition from desktop PC towards small form factor systems in deploying home technologies. The term small form factors (SFF) refers to computer with a smaller footprint. This means that a small form factor system has the exact features as their desktop counterpart such as memory, flash storage, processor, integrated audio and video and so forth. However, in most cases, small form factors usually have limited expansion options due to their smaller size. Pioneers like VIA Technologies™ and Soekris Engineering™ introduces low power and general purpose small form factor systems for individual users. The use of small form factor systems as the core infrastructure in home environment is predicted to be the next gigantic leap in realizing invisible computing paradigm. In realizing invisible computing for home systems, the computers or processing unit should stay out of sight and do their respective tasks. Small form factors could realize the invisible computing goals for home systems due to its smaller size and less setup hassles, makes it an ideal solution for application deployment in home environment. Although the introduction of small form factors isn’t new in computing arena, it has already been primary choice for home entertainment systems, gaming consoles and home gateways. Industrial giants are predicting that small form factors are getting powerful and flexible enough that it could replace multiple devices in home environment near future. Incredible developments in bus speed and CPU could soon move small form factors to greater heights and extending to diversified applications.

There are many types of small form factors systems ranging from cubical or flat size, mini-ITX and bookshelf computers. Figure 1 shows the various sizes of ITX form factors.

Figure 1: Various Sizes of ITX Form Factors

Small form factors are generally categorized as slim or cube-shaped. Cubed models are larger but provide expandability. This includes cubed model comes with integrated audio and video onto single motherboard but at same time provides PCI slots to install dedicated cards. On the other hand, slim models offer similar features and focus on extremely high power efficiency. Small form factors come in prebuilt and barebones units, with the latter integrated with casing, motherboard, and power supply as well as options for users on choosing their dedicated components especially on RAM, hard disk and other PCI cards depending on the application requirement.

There are many small form factors that is available in the market and widely fielded by three standards; PC/104, EBX and System-On-Module (SOM).


PC/104 is referred as an expandable format. Application developers can use PC/104 as single board computer, a mezzanine or an expansion bus based on their requirements. The size of PC/104 is small (3.55″ x 3.78″) and usually based on lower end 32-bit x86 processors. The PC/104 standard provides ISA bus connectivity through a special PC/104 connector. One of the main advantage of PC/104 is it allows peripheral modules to be stacked one on top of another so that almost any applications can be implemented with a PC/104 module stack. PC/104 format will run any operating system with any programming language. A specification called PC/104-Plus was introduced by the PC/104 Embedded Consortium to support higher PCI based bus connections that fits some industrial application requirement. Figure 2 below shows an example of PC/104 module.

Figure 2: PC/104 Module


Embedded Board eXpandable (EBX) is one of the larger versions (5.75″ x 8.0″) of small form factors. Normally tailored for higher-end processors and at same time low-end processors boards for EBX are also available. EBX boards are closer to their desktop PC counterpart as it has all the features of personal computer like digital I/O, audio, analog and so forth. The larger size of EBX also enables Pentium class CPUs fit and requisite cooling fan on a single board. EBX supports both PC/104 and PC/104 Plus. Similar to PC/104, EBX form factor will run on any operating system with any programming language. Since EBX form factor are larger, they usually accommodate four serial ports, four or more USB ports as well as Ethernet ports.


A new standard called as System-on-Module (SOM) or sometimes referred as Computer-On-Module (COM) was introduced recently. System-on-Module is targeted for full bespoke solution that would need large engineering design effort. A System-on-Module approach comprises two components: processor module and the carrier board. The off-the-shelf processor module contains the processor module that places the processor, real-time clock, serial ports, memory, Ethernet, hard disk or flash disk and other digital I/O. The processor module plugs into carrier board, which provides all the system connectors and any additional I/O components required for the application. The advantage of a System-on-Module design is that it can decrease the cabling requirement and expansion module stacking found in existing small form factors, as well as saving the system unit costs. In System-on-Module design, reliability of the entire system is enhanced by reducing cabling and module interconnections. ETX, COM Express, XTX, and STX are examples of System-on-Module standards covered by the ETX Industrial Group (, PICMG (, the XTX Consortium (, and the STX Consortium ( respectively.


The best part with small form factors are that they are already has several essential features for home systems solutions that ensure performance and reliability in managing heterogeneous applications. These small form factors are ideal for home environment due to their characteristics and desirable features like:

Extensibility: their smaller modular size enables extension to various home applications like access points and surveillance systems as well as wide range of digital and analog I/O modules. For digital surveillance, home user might want to place a computer in a closet, up in the ceiling or outside living room. Compact and smaller size of small form factors provides maximum versatility in the home environment. Another good example would be home media centers in small form factor that are very popular because they blend in compact dimensions and power of desktop PC.

Compatibility among multiple computing systems: One of the common characteristic of small form factor system is that they can run both proprietary and open source operating systems (Linux, BSD Unix and others). This characteristic suits the requirement of home technologies as they are bunch of myriad applications with different platform and operating systems. Also, wired and wireless connections are integrated in small form factors for hybrid connectivity; Home network gateways are good example that includes a single unit of small form factor to serve an entire home network.

Scalability: Small form factor computers have wide spectrum of CPU types that allows easy scalability towards better performances for various home applications. For instance, additional module for numerous applications can be extended using PC/104 module stack.

Power management: The requirement of many small form factor systems are low enough and could provide a 24×7 uninterruptible supplies. This is an important criterion for home systems especially for safety critical sub-systems like health monitoring that need to be in continuous operation. The requirements of some small form factors are low enough that technology like power over Ethernet (PoE) (which delivers a maximum of 12.95watts) is possible to be utilized for home systems.

Heat Small form factors systems generate less heat as many of them operates without any fans at all.

Noise: Noise in most computers comes from moving parts that spin like hard drives and fans. Small form factors have no moving parts and their processors are passively cooled. For persistent storage, small form factors uses flash memory instead of hard disks

Invisible computing: Finally, small form factors could realize the prospect of invisible computing in smart home environment to become more realistic.

Currently, the Small Form Factor Special Interest Group (SFF-SIG) is taking care of small form factor standards development focusing on advantages of the I/O and bus interfaces. With more developments and availability of small form factors in market, home systems application are also expected to grow and benefit home dwellers in near future.

PC/104 and Small Form Factors –

Small Form Factor Special Interest Group (SFF-SIG) –

Duane Wessels and Matthew J.Weaver, ” Small Form Factor PCs”, O’Reilly April 2008

Eric Rossi, “An I/O view of small form factor choices”, PC/104 and Small Form Factors,2007,OpenSystems Publishing –

PC/104 Embedded Consortium, –

About the Author:
Thinagaran Perumal is pursuing his PhD in Smart Technology and Robotics and attached with Institute of Advanced Technology, University Putra Malaysia. He has been involved in research areas of middleware technologies and interoperability for smart home environment. He can be reached at