Product guide

138
Appendix C Glossary
DIMM: Dual In-line Memory Module. Small circuit boards carrying
memory integrated circuits, with signal and power pins on both
sides of the board, in contrast to single-in-line memory modules
(SIMM). On a DIMM, the connections on each side of the module
connects to different chips. This allows for a wider data path, as
more modules can be accessed at once.
DIN: Deutsch Industrie Norm. A round multi-pin connector,
generally used to connect the keyboard and mouse to the system.
Disk: Storage medium. See “Compact Disc,” “Floppy Disk,” “Hard
Disk,” and “Removable Storage”.
Disk-Imaging: The creation of a template copy of a system
software configuration for later transfer to selected workstations.
The disk image is created to include the OS, hard drive partitions,
FAT structure, and selected software; usually without the drivers
for particular components, which must be added later. Once the
image is created it can be transferred over a network for automatic
installation to client workstations. Also called "ghosting."
Disk Mirroring: The recording of redundant data for fault tolerant
operation. Data is written on two partitions of the same disk, on
two separate disks within the same system or on two separate
computer systems.
DMA: Direct Memory Access. A method for transferring data
directly to and from system memory, bypassing the
microprocessor.
DMI: Desktop Management Interface. An interface for managing
computers by providing information about the system and its
components to DMI-compliant viewers.
DRAM: Dynamic Random Access Memory. Memory that requires
a periodic refresh cycle to keep the stored information from being
lost. Loss of power causes loss of data in this memory.
DSTN: Double Super-Twisted Nematic or Dual-Scan Twisted
Nematic. DSTN displays utilize dual-scan, passive matrix
screen technology. The contrast ratio that goes as high as 30-
to-1, and glare resistance ("washing out") is improved over
earlier DSTN screens. But refresh rate is slower than with
active matrix, or Thin Film Transistor (TFT), technology displays,
which means DSTN is less desirable for motion video or
animation. Supertwist refers to a technique for improving LCD
display screens by twisting light rays. In addition to normal
supertwist displays, there also exist double supertwist and triple
supertwist displays. In general, the more twists, the higher the
contrast. Dual scan refers to the process of refreshing the
screen twice as fast as conventional passive matrix displays.
Dual-scan displays are not as sharp or bright as active-matrix
displays, but they consume less power.
Duplexing: Duplexing has all the benefits of mirroring but adds
further protection utilizing different disk channels to connect two
drives in a mirrored set. Often this is done using two SCSI
controllers, one to each SCSI drive.
DVD: Digital Versatile Disc. A DVD disc is a high-density disc
that holds large amounts of digital data for playback on a variety
of electronic mediums; including DVD players, computers, audio
CD players, etc. The DVD format presents cinema quality
picture and sound via interactive menus. There are several
existing DVD format standards: DVD-One layer, one side-4.5
GB; DVD-9 -One layer, dual sided-9 GB; DVD-10 -Two layers,
each dual sided-17 GB; DVD-ROM -Designed for use in a
computer and encompasses all formats.
ECC: Error Checking and Correction. Detects errors in
transmitted data and attempts to correct them on the fly. The
simplest form of error detection is a single added parity bit or a
cyclic redundancy check. Multiple parity bits not only detect
that an error has occurred, but also which bits have been
inverted and should therefore be re-inverted or fixed to restore
the original data.