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U
Ultra DMA
A protocol developed by Quantum Corporation and Intel that supports burst mode data
transfer rates of 33.3 MBps. This is twice as fast as the previous disk drive standard for PCs,
and is necessary to take advantage of new, faster Ultra ATA disk drives. The official name
for the protocol is Ultra DMA/33. Follw-on, more advanced protocols include
Ultra DMA/66 and Ultra DMA/100, which support burst mode data transfer rates of
66 MBps and 100 MBps, respectively.
USB
Universal Serial Bus. An external bus standard that supports data transfer rates of 12 Mbps
(12 million bits per second). 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. It is expected to eventually replace serial and parallel ports.
V
VESA
Video Electronics Standards Association. The source of a SuperVGA standard used on
many video boards.
virus
Software that copies itself onto hard drives and diskettes without user intervention, usually
when a diskette is placed into the drive of a computer. Viruses trigger a harmless or
destructive occurrence on the system, activated by some preset condition. Viruses are
frequently written with antisocial intent.
VGA
Video Graphics Array. Graphics technology that supports up to 256 K colors and a graphics
resolution of 640 by 480 pixels.
volatile memory
Storage media that loses its data when system power is turned off. Standard memory and
memory added to the system are volatile memory. See nonvolatile memory.
VRAM
Video RAM. VRAM is special-purpose memory used by video adapters. Unlike
conventional RAM, VRAM can be accessed by two different devices simultaneously. This
enables a video adapter to access the VRAM for screen updates at the same time that the
CPU provides new data. VRAM yields better graphics performance but is more expensive
than normal RAM. A special type of VRAM, called Windows RAM (WRAM), yields even
better performance than conventional VRAM. See SGRAM and WRAM.
W
warm boot
Process of resetting the computer without turning off the power through keyboard input
(pressing Ctrl, Alt, and Del keys simultaneously) or the reset button. The system returns to
an initial or arbitrarily selected condition.
14 Glossary
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