GLOSSARY- Rackmount Computer


Storage Device
Expansion Slots
Power Supply
ATX Power

Drive Bays
Cooling Fan
Watchdog Timer
USB 2.0
Gigabit Ethernet

The chassis is the enclosure that contains the main components of a computer. A computer case is sometimes incorrectly referred to metonymously as a CPU or hard drive referring to components housed within the case. CPU was a more common term in the earlier days of home computers, when peripherals other than the motherboard were usually housed in their own separate cases. They are usually constructed from steel (often SECC—Steel, Electrically Chromate Coated) or aluminium. Plastic is sometimes used, and other materials such as wood and even Lego blocks have appeared in home-built cases. The chassis can come in many different sizes and usually determined by the form factor of the motherboard. Currently, the most popular form factor for desktop computers is ATX, although microATX and small form factors have also become very popular for a variety of uses.

Storage Device:
A storage device, often called storage or memory, refers to computer components and recording media that retain digital data used for computing for some interval of time. Computer data storage provides one of the core functions of the modern computer, that of information retention. It is one of the fundamental components of all modern computers, and coupled with a central processing unit (CPU, a processor), implements the basic computer model used since the 1940s.

In contemporary usage, memory usually refers to a form of semiconductor storage known as random-access memory (RAM) and sometimes other forms of fast but temporary storage. Similarly, storage today more commonly refers to mass storage — optical discs, forms of magnetic storage like hard disk drives, and other types slower than RAM, but of a more permanent nature. Historically, memory and storage were respectively called main memory and secondary storage (or auxiliary storage). Auxiliary storage (or auxiliary memory units) was also used to represent memory which was not directly accessible by the CPU (secondary or tertiary storage). The terms internal memory and external memory are also used.
Expansion Slots :
An Expansion Slot is an opening in a computer where a circuit board can be inserted to add new capabilities to the computer. Nearly all personal computers except portables contain expansion slots for adding more memory, graphics capabilities, and support for special devices. The boards inserted into the expansion slots are called expansion boards, expansion cards , cards , add-ins , and add-ons. Expansion slots for PCs come in two basic sizes: half- and full-size. Half-size slots are also called 8-bit slots because they can transfer 8 bits at a time. Full-size slots are sometimes called 16-bit slots. In addition, modern PCs include PCI slots for expansion boards that connect directly to the PCI bus.
Power Supply :
Power supply is a supply of electrical power. A device or system that supplies electrical or other types of energy to an output load or group of loads is called a power supply unit or PSU. The term is most commonly applied to electrical energy supplies, less often to mechanical ones, and rarely to others. A power supply may include a power distribution system as well as primary or secondary sources of energy such as: C.M.S
Mounting, in computing, is the process of making a file system ready for use by the operating system. The term's historical basis refers to a period when the medium being mounted was physically placed (mounted) in the device before using it.
ATX Power :
ATX (Advanced Technology Extended) is a computer form factor designed by Intel in 1995. It was the first big change in computer case, motherboard, and power supply design in many years. ATX overtook AT completely as the default form factor for new systems. ATX addressed many of the AT form factor's annoyances that had frustrated system builders. Other standards for smaller boards (including microATX, FlexATX and mini-ITX) usually keep the basic rear layout but reduce the size of the board and the number of expansion slot positions. In 2003, Intel announced the BTX standard, intended as a replacement for ATX. As of 2009[update], the ATX form factor remains a standard for do-it-yourselfers; BTX has however made inroads into pre-made systems. The official specifications were released by Intel in 1995, and have been revised numerous times since, the most recent being version 2.3, released in 2007. A full size ATX board is 12 in × 9.6 in (305 mm × 244 mm). This allows many ATX form factor chassis to accept microATX boards as well.
Drive Bays :
A drive bay is a standard-sized area for adding hardware to a computer. Most drive bays are fixed to the inside of a case, but some can be removed. Over the years since the introduction of the IBM PC, it and its compatibles have had three types of drive bay, of which two are in common use today. Full-height bays were found in old PCs in the early to mid-1980s. They were approximately 3.5" high by 5.75" wide, and used mainly for hard disks and floppy disk drives. Half-height drive bays are approximately 1.75" high by 5.75" wide, and are the standard housing for CD and DVD drives in modern computers, but were sometimes used for other things, including hard disks and floppy disk drives in the past. It is important to note that the name does not refer to the width of the bay itself, but rather to the width of the disks used by the floppy drives which mounted in these bays. Often represented as 5¼-inch. 3.5" bays, like their larger counterparts, are named after diskette dimensions; their actual dimensions are 4" wide by 1" high. Those with an opening in the front of the case are generally used for floppy or Zip drives. Hard drives in modern computers are typically mounted in fully internal 4" (nominally 3.5") bays. Of course, nowadays most computers - especially laptops - don't come with floppy drives at all since CD/DVD-RW drives are very common. There are adapters, sometimes called a "sled", which can be used to mount a 3.5" device in a 5.25" bay. Often represented as 3½-inch.
Cooling Fan:
A computer fan is any fan inside a computer case used for cooling purposes, and may refer to fans that draw cooler air into the case from the outside, expel warm air from inside, or move air across a heatsink to cool a particular component. The use of fans to cool a computer is an example of active cooling. As processors, graphics cards, RAM and other components in computers have increased in clock speed and power consumption, the amount of heat produced by these components as a side-effect of normal operation has also increased. These components need to be kept within a specified temperature range to prevent overheating, instability, malfunction and damage leading to a shortened component lifespan. While in earlier personal computers it was possible to cool most components using natural convection (passive cooling), many modern components require more effective active cooling. To cool these components, fans are used to move heated air away from the components and draw cooler air over them. Fans attached to components are usually used in combination with a heatsink to increase the area of heated surface in contact with the air, thereby improving the efficiency of cooling. 
Watchdog Timer:
A watchdog timer (or computer operating properly (COP) timer) is a computer hardware or software timer that triggers a system reset or other corrective action if the main program, due to some fault condition, such as a hang, neglects to regularly service the watchdog. The intention is to bring the system back from the nonresponsive state into normal operation. Watchdog timers can be more complex, attempting to save debug information onto a persistent medium; i.e. information useful for debugging the problem that caused the fault. In this case a second, simpler, watchdog timer ensures that if the first watchdog timer does not report completion of its information saving task within a certain amount of time, the system will reset with or without the information saved. The most common use of watchdog timers is in embedded systems, where this specialized timer is often a built-in unit of a microcontroller. For those embedded systems that can't be constantly watched by a human, watchdog timers may be the solution.
USB 2.0:
Released in April 2000. Added higher maximum bandwidth of 480 Mbit/s (now called "Hi-Speed"). USB is intended to help retire all legacy varieties of serial and parallel ports. USB can connect computer peripherals such as mouse devices, keyboards, PDAs, gamepads and joysticks, scanners, digital cameras, printers, personal media players, and flash drives. For many of those devices USB has become the standard connection method. USB is also used extensively to connect non-networked printers; USB simplifies connecting several printers to one computer. USB was originally designed for personal computers, but it has become commonplace on other devices such as PDAs and video game consoles. In 2004, there were about 1 billion USB devices in the world. The design of USB is standardized by the USB Implementers Forum (USB-IF), an industry standards body incorporating leading companies from the computer and electronics industries. Notable members have included Apple Inc., Hewlett-Packard, NEC, Microsoft, Intel, and Agere.

Gigabit Ethernet:
There are four different physical layer standards for gigabit Ethernet using optical fiber (1000BASE-X), twisted pair cable (1000BASE-T), or balanced copper cable (1000BASE-CX). Half-duplex gigabit links connected through hubs are allowed by the specification but in the marketplace full-duplex with switches are normal. Ethernet has evolved into the most widely implemented physical and link layer protocol today. Gigabit Ethernet, also known as GbE or 1 GigE, is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second. Fast Ethernet increased speed from 10 to 100 megabits per second (Mbit/s) and Gigabit Ethernet was the next iteration, increasing the speed to 1000 Mbit/s. The initial standard for gigabit Ethernet was produced by the IEEE in June 1998 and required optical fiber.
VGA, PS/2:
Video Graphics Array (VGA) through its widespread adoption has also come to mean either an analog computer display standard, the 15-pin D-subminiature VGA connector or the 640×480 resolution itself. While this resolution was superseded in the personal computer market in the 1990's, it is becoming a popular resolution on mobile devices. VGA was the last graphical standard introduced by IBM that the majority of PC clone manufacturers conformed to, making it the lowest common denominator that all PC graphics hardware supports, before a device-specific driver is loaded into the computer today. For example, the MS-Windows splash screen appears while the machine is still operating in VGA mode, which is the reason that this screen always appears in reduced resolution and color depth. VGA was officially superseded by IBM's XGA standard, but in reality it was superseded by numerous slightly different extensions to VGA made by clone manufacturers that came to be known collectively as "Super VGA".

The PS/2 connector is used for connecting some keyboards and mice to a PC compatible computer system. Its name comes from the IBM Personal System/2 series of personal computers, with which it was introduced in 1987. The PS/2 mouse connector generally replaced the older "serial mouse" connector, while the PS/2 keyboard connector replaced the larger 5-pin DIN. The PS/2 designs on keyboard and mouse interfaces are electrically similar and employ the same communication protocol. However, a given system's keyboard and mouse port may not be interchangeable since the two devices use a different set of commands. Following the release of USB keyboards, PS/2 keyboards and mice have become less popular.