Definitions for Computer Modding and Form Factor

Computer Modding

Computer modding (that is, modification) has grown by leaps and bounds into its current standing as a strong and growing industry. Websites such as Cool Case Gallery ( demonstrate computer modding, which is also known as case modding.

Basic case modding entials adding a window to the side of the case to show the parts inside. The case's interior is usually illuminated by cold cathode lights which get their power from a spare molex connector.

Also, many attempt their own case mods, using switches at the front as well as LCDs. These may control fan speeds, temprature of the case, or other information.

Form Factor for Computer Cases

Form factor refers to the linear dimensions and configuration of a device as distinguished from other measures of size (for example Gigabytes; a measure of storage size):

In computing, form factor is used to describe the size and format of PC motherboards (see AT, ATX, BTX), but also of hard drives, power supplies, cases, and add-in cards. The term can also be used refer to the shape of a housing or package or mechanical connection associated with a device or mechanism within the context of its interface with other devices or mechanisms, also in regards to a human interface.

ATX Computer Case Form Factor

The ATX form factor was created by Intel in 1995. It was the first big change in computer case and motherboard design in many years. ATX overtook AT completely as the default form factor for new systems. Some related designs include mini-ATX and micro-ATX. ATX addressed many of the annoyances with the AT form factor that system builders had to put up with. ATX will be replaced by BTX.

AT-style computer cases had a power button that was directly connected to the system power supply unit (PSU). The general configuration had four pins that had to be connected individually. Sometimes, the pins were soldered to the power button, making it difficult to replace the power supply if it failed, or if the fan inside the PSU seized up. The ATX version of the power supply didn't directly connect to the system power button, allowing the computer to be powered off via software. However, many ATX power supplies have a switch on the back to ensure no power is flowing to the motherboard (a trickle of energy is normally sent to an ATX-style motherboard even if the computer appears to be "off").

The power supply's connection to the motherboard was changed. Older AT power supplies had two similar-looking connectors that could sometimes inadvertently be plugged in incorrectly, generally causing short-circuits in the motherboard and causing it to fail. ATX used one large keyed connector instead, which made installation much easier and safer. However, the amount of power delivered fell below the requirements of newer AGP video cards and faster processors such as Intel's Pentium 4 and Advanced Micro Devices's Athlon, so some auxiliary power connectors were eventually added to the standard.

On the back of the system, some major changes were made. The AT standard only had a keyboard connector and little else. Other common data connectors such as serial and parallel ports had to be mounted individually. ATX allowed each motherboard manufacturer to put these ports in a rectangular area on the back of the system, with an arrangement they could define themselves (though a general pattern has been followed by most manufacturers). To avoid any gaps in the case, each manufacturer provided their own rear panel that could be inserted and fill any unused space.

The ATX form factor uses an 20-pin power connector located on the motherboard. The newest ATX specification uses a 24-pin power connector to support the power requirements of PCI Express.

--- Paul LoIacono is the president and owner of ATX Cases. You can see a wild array of computer case shapes, sizes and designs by visiting

Paul LoIocano