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Appendix II: 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 at only 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 Packet 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, then, also results in greater speed.
BBS (BIOS Boot Specification):
is 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 fails for some reason. 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, and provides the
basic instructions for controlling your computer’s hardware. Both the operating 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 manipulate data
in a buffer before copying it, all at once, 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 also the possibility of losing your data should the system crash. Information stored 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 needed information is stored in the SRAM instead of in
the slow 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.
