NEC SP B-Series - Manual (Page 138)

16 Glossary
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.
WRAM
Windows RAM. A type of RAM that supports two ports. This enables a video
adapter to fetch the contents of memory for display at the same time that new bytes
are being pumped into memory. This results in much faster display than is possible
with conventional single-port RAM. WRAM is similar to VRAM, but achieves
even faster performance at less cost because it supports addressing of large blocks
(windows) of video memory. See VRAM and SGRAM.
write
To record or store information to a storage device.
write-back
Also called copy back. A cache strategy where write operations to data stored in the
internal microprocessor L1 cache aren’t copied to system memory until absolutely
necessary. In contrast, a write-through cache performs all write operations in
parallel; data is written to system memory and the L1 cache simultaneously. Write-
back caching yields somewhat better performance than write-through caching
because it reduces the number of write operations to main memory. See cache and
write-through.
write-through
Also write-thru. Write-through characterizes a cache strategy where data is always
written into system memory when data is written by the CPU. See cache and write
back.
X
X2 technology
A technology developed by U.S. Robotics (now 3Com) for delivering data rates up
to 56 Kbps over plain old telephone service (POTS). It was long believed that the
maximum data transmission rate over copper telephone wires was 33.6 Kbps, but
X2 achieves higher rates by taking advantage of the fact that most phone switching
stations are connected by high-speed digital lines. X2 bypasses the normal digital-
to-analog conversion and sends the digital data over the telephone wires directly to
a modem where it is decoded.