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Appendix I: Glossary
ACPI (Advanced Configuration and Power Interface): a power management specification that
allows the operating system to control the amount of power distributed to the computer's devices.
Devices not in use can be turned off, reducing unnecessary power expenditure.
AGP (Accelerated Graphics Port): a PCI-based interface which was designed specifically for
demands of 3D graphics applications. The 32 -bit AGP channel directly links the graphics controller
to the main memory. While the channel runs only at 66 MHz, it supports data transmission during
both the rising and falling ends of the clock cycle, yielding an effective speed of 133 MHz.
ATAPI (AT Attachment Packe t Interface): also known as IDE or ATA; a drive implementation
that includes the disk controller on the device itself. It allows CD -ROMs and tape drives to be
configured as master or slave devices, just like HDDs.
ATX: the form factor designed to replace the AT form factor. It improves on the AT design by
rotating the board 90 degrees, so that the IDE connectors are closer to the drive bays, and the
CPU is closer to the power supply and cooling fan. The keyboard, mouse, USB, serial, and
parallel ports are built-in.
Bandwidth: refers to carrying capacity. The greater the bandwidth, the more data the bus, phone
line, or other electrical path can carry. Greater bandwidth results in greater speed.
BBS (BIOS Boot Specification): a feature within the BIOS that creates, prioritizes, and maintains
a list of all Initial Program Load (IPL) devices, and then stores that list in NVRAM. IPL devices
have the ability to load and execute an OS, as well as provide the ability to return to the BIOS if
the OS load process fa ils. At that point, the next IPL device is called upon to attempt loading of
the OS.
BIOS (Basic Input/Output System): the program that resides in the ROM chip, which provides
the basic instructions for controlling your computer's hardware. Both the opera ting system and
application software use BIOS routines to ensure compatibility.
Buffer: a portion of RAM which is used to temporarily store data; usually from an application
though it is also used when printing and in most keyboard drivers. The CPU can ma nipulate data
in a buffer before copying it to a disk drive. While this improves system performance (reading to or
writing from a disk drive a single time is much faster than doing so repeatedly) there is the
possibility of losing your data should the system crash. Information in a buffer is temporarily
stored, not permanently saved.
Bus: a data pathway. The term is used especially to refer to the connection between the
processor and system memory, and between the processor and PCI or ISA local buses.
Bus mastering: allows peripheral devices and IDEs to access the system memory without going
through the CPU (similar to DMA channels).
Cache: a temporary storage area for data that will be needed often by an application. Using a
cache lowers data access times since the information is stored in SRAM instead of slower DRAM.
Note that the cache is also much smaller than your regular memory: a typical cache size is
512KB, while you may have as much as 4GB of regular memory.
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