BIOS

The acronym B.I.O.S. stands for Basic Input Output System, the software that manages the basic set of functions the computer must perform without accessing any software programs from the hard disk. The BIOS contains the instructions required to control the keyboard, monitor display, hard drives, serial communications, as well as some other various basic functions. The BIOS is responsible for the basic set of data transactions that permit the computer to start up (called "booting").

The BIOS is stored in a Read Only Memory (ROM) chip that is soldered onto the motherboard. This ensures that the BIOS will always be available and will not be damaged by mechanical disk failures or data corruption.

Because Random Access Memory (RAM) is faster than Read Only Memory (ROM), many hardware manufacturers design systems so that the BIOS code is copied over from the ROM to the RAM when the computer is booted. This technique is known as "shadowing" and permits a substantial increase in performance.

Modern PCs have what is known as a "Flash BIOS", which is a BIOS recorded in a flash memory chip which can be updated as necessary. Many common computer problems in PCs that have been in operation for a year or more can be solved by upgrading the BIOS this way. Caution is necessary however as a corrupted BIOS will render the computer unbootable.

A BIOS that can recognize and appropriately configure the system to use a Plug-and-Play (PnP) device is known as PnP BIOS (or PnP aware).

EFI

EFI is an acronym for Extensible Firmware Interface, which is basically a newer software design meant to replace the older BIOS standard.

The new Intel-based Apple Macintosh computers use an EFI instead of the traditional PC BIOS. At this point in time, early 2006, the basic incompatibility between BIOS and EFI is the only reason why Microsoft Windows cannot be installed on a Mac.

The EFI specification defines a model for the interface between the operating system and firmware, basically meaning the it handles the relationship between the OS and the hardware, although that's very simplified way of describing it.

The EFI interface consists of platform-related information, boot ("starting up") and runtime ("the OS is running") services for the operating system and its loader. Together, these provide a standard for running the pre-boot applications and then booting the operating system.

Firmware

Software that has been written onto read-only memory (ROM) hardware chips that define the basic set of code that the BIOS must be aware of in order to understand what hardware it is dealing with.

Loader

The piece of software that permits the Operating System to load into memory and become active, thereby letting the computer start the OS and leave the BIOS-only part of the starting-up process behind.

CMOS

An acronym for Complementary Metal Oxide Semiconductor.

CMOS is a widely used type of semiconductor. Personal computers have a small battery powered CMOS memory chip to hold the date, time, and system setup parameters while the computer is powered off.

When your computer suddenly starts saying that the date is January 1 1990, it is because your CMOS battery died and the system forgot what date it is.

AGP

An acronym for Accelerated Graphics Port, a video hardware interface specification developed by Intel.

AGP is based on PCI, but is designed especially for the high speed demands of 3-D video graphics. Rather than using the PCI bus for graphics data, AGP introduces a special video-only channel so that the graphics card can directly access main memory. The AGP 1x channel is 32 bits wide and runs at 266 MBps, which is twice as fast as PCI. Other upgraded versions of AGP run at 2X (533 MBps) and 4X provides 1.07 GBps.

To install an AGP video card, your system must:

• Have a chipset that supports AGP.

• The motherboard must be equipped with an AGP slot (which is brown, and you have only one on the motherboard). AGP video cards will not fit in a PCI slot.

• The operating system must be Windows 95 SR2.1, Windows 98 or Windows NT 4.0 or above.

• Macintoshes built after September 1999 and using Mac OS 8.6 or above support AGP.

• AGP video cards are not cross-platform (Mac / Windows) compatible.

PCI

An acronym for Peripheral Component Interconnect, developed by Intel Corporation.

A bus is the set of wired conenctions through which data is transmitted from one part of a computer to another. A bus is often compared to a highway on which information signals travel throughout a computer connecting the internal computer components to the CPU and main memory (the "internal" bus).

The PCI expansion bus permits cards that are added to the sytem to access the CPU and memory. Modern PCs and Macs use PCI busses (as opposed to the previous ISA expansion bus technology used in PCs or NuBus on Macs).

PCI is a 64-bit bus, though it is often implemented as a 32-bit bus. It can run at clock speeds of 33 or 66 MHz.

PCI-X and PCI Express

PCI extended, an enhanced PCI bus.

PCI-X is backward-compatible with existing PCI cards. It increases the speed of PCI from 133 MBps to as much as 1 GBps. PCI-X was designed to increase performance of high bandwidth devices such as Gigabit Ethernet and Fibre Channel.

PCI Express (different from PCI-X) doubles the data transfer rates of the original PCI bus, which works out to transfer rates of approximately 200MB/s. PCI Express was also developed so that high-speed interconnects such as 1394b, USB 2.0, InfiniBand and Gigabit Ethernet would have an I/O architecture suitable for their transfer high speeds.

USB

An acronym for Universal Serial Bus, an external bus standard that supports data transfer rates of 12 Mbps (USB 1) up to 480 Mbps (USB 2).

A single USB port can be used to connect up to 127 peripheral devices, such as mice, modems, and keyboards. USB also supports Plug-and-Play installation and hot plugging.

USB appeared in 1996, but it wasn't until the release of the best-selling Apple iMac in 1998 that USB became widespread. It is expected to completely replace serial and parallel ports, although even in 2006 PCs still ship with these old ports.

USB 2 "Hi-Speed USB" was developed as an answer to Apple's FireWire technology.

Firewire / IEEE 1394

A very fast external bus that supports data transfer rates of up to 400Mbps (in 1394a) and 800Mbps (in 1394b).

Apple, which originally developed the technology, uses the name FireWire. Other companies use names such as i.link and Lynx.

In addition to high speed, 1394 also delivers data at a guaranteed rate ("isochronous"). This makes it ideal for devices that need to transfer lots of data in real-time, such as video and audio. Although extremely fast, FireWire is quite expensive and has thus let USB gain a large market share.

Like USB, 1394 supports both Plug-and-Play and hot plugging, and also provides power to peripheral devices. A single 1394 port can be used to connect up 63 external devices.

Parallel Port

An interface for connecting an external device such as a printer.

Most personal computers have both a parallel port and at least one serial port, in addition to more modern bus connectors like FireWire and USB. On PCs, the parallel port is today used to connect to older printers, although it used to be used to connect to other devices as well (cameras, other computers, etc).

The parallel port is sometimes referred to as a "Centronics" port after the company that designed the original parallel communication standard. The modern parallel design is based on Epson's version.

Serial port

A pretty much obsolete port, or interface, design in which only 1 bit is transmitted at a time. The serial port was a general-purpose interface that could be used for almost any type of device, including modems, mice, and printers although printers more often used the parallel port instead.

CPU

An acronym for Central Processing Unit.

The CPU is the brain of the computer since it is where most calculations take place. In so far as it literally does the "computing", the CPU is the most important element of the computer system. The CPU is housed in a single chip called the microprocessor.

Newer CPU designs are now becoming common where "Dual Core" chips actually have two CPUs built in to the same microprocessor die. This is a cheaper way to build dual processor machines than actually having two CPUs put side by side on the motherboard.

Ethernet (RJ-45)

PS/2 ports

RAM

IDE

CDROM

DVDROM