| UltraDMA
(UDMA) |
Ultra
DMA/66 (DMA = Direct Memory Access) is the successor of Ultra DMA/33. Ultra
DMA/66 doubles the bus transfer rate of Ultra DMA/33 to 66.6 MB/s (Ultra
DMA/33 = 33.3 MB/s). As with Ultra DMA/33, CRC (Cyclic Redundancy Check)
verifies the integrity of transferred data. |
| UltraSCSI |
This is
an old term for the FAST-20 data rate. This term was dropped by the ANSI
committee because the company UltraStore owned a trademark on the term Ultra
SCSI, so it could not be used by the standards committee to describe its
work. If you see this term anywhere, read carefully to see if it refers
to the UltraStore trademark (which refers to a SCSI FAST class of product)
or if the writer is incorrectly using this term for FAST-20. |
| Unformatted
Capacity |
The total
number of usable bytes on a disk, including the space that will be required
to later to record location, boundary definitions, and timing information.
(See formatted capacity for comparison.) |
| USB |
Short
for 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. |
| USB
2.0 |
Universal
Serial Bus High Speed is the next generation of Universal Serial Bus and
is 40X faster than USB 1.1 with a transfer rate of 480 Mbps. USB 2.0 will
allow all sorts of new and improved USB devices to be added to the USB product
lineup such as fast disk drives, CDRW's, High Quality Video Cameras, and
High Speed Scanners. |
| VAR |
Value
Added Reseller. |
| VME
Bus |
The VersaModule
Eurocard bus is a 32-bit bus developed by Motorola, Signetics, Mostek and
Thompson CSF. It is widely used in industrial, commercial and military applications
with over 300 manufacturers of VMEbus products worldwide. VME64 is an expanded
version that provides 64-bit data transfer and addressing. |
| Volatile
Memory |
Memory
that may not retain data written to it for a subsequent read operation through
a power-on condition. An example of this is a silicon memory device that
loses data written to it if device power is lost. |
| WAN |
Wide
Area Network. |
| WDM |
Wavelength
Division Multiplexer. |
| Write
Back |
Data written
into the cache by the CPU is not written into main memory until that data
line in the cache is to be replaced. Also referred to as Copy Back. |
| Write
Through |
A
technique for writing data from the CPU simultaneously into the cache and
into main memory to assure coherency. |
