Specifications

Glossary
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Xeon Intel’s family name for its server processors
derived from the Pentium II, Pentium III, and
Pentium 4 desktop processors. The Pentium II Xeon
and Pentium III Xeon use Slot 2, whereas Xeon (the
Pentium 4 version does not have a numerical desig-
nation) uses the Socket 603 or Socket 604. All Xeon
processors have larger caches and memory address-
ing schemes than their desktop counterparts. Some
Xeon processors support EM64T 64-bit extensions,
and a dual-core version of Xeon with EM64T sup-
port was introduced in the first quarter of 2006.
Xeon MP A version of the Intel Xeon made espe-
cially for four-way and larger server implementa-
tions. Some versions of the Xeon MP support
EM64T 64-bit extensions, and a dual-core version
with EM64T support was introduced in the first
quarter of 2006.
XGA (extended graphics array) A type of PC
video display circuit (and adapter) first introduced
by IBM on October 30, 1990, that supports text and
graphics. Text is supported at a maximum resolu-
tion of 132×60 characters in 16 colors with a char-
acter box of 8×6 pixels. Graphics are supported at a
maximum resolution of 1024×768 pixels in 256
(from a palette of 262,144) colors or 640×480 pixels
in 65,536 colors. The XGA outputs an analog signal
with a horizontal scanning frequency of 31.5KHz
or 35.52KHz and supports analog color or analog
monochrome displays. Also used to refer generi-
cally to any adapter or display capable of 1024×768
resolution.
XML (Extensible Markup Language) A stan-
dard for creating and sharing data and data formats
over the Internet and other networks. XML, like
HTML, uses markup tags to control the page, but
XML tags control both appearance and the uses of
the data and can be extended with new tags created
by any XML user. See also W3C.
XMM (extended memory manager) A driver
that controls access to extended memory on 286
and later processor systems.
HIMEM.SYS is an exam-
ple of an XMM that comes with DOS and
Windows 9x.
XModem A file-transfer protocol—with error
checking—developed by Ward Christensen in the
mid-1970s and placed in the public domain.
Designed to transfer files between machines run-
ning the CP/M operating system and using 300bps
or 1,200bps modems. Until the late 1980s, because
of its simplicity and public-domain status,
XModem remained the most widely used micro-
computer file-transfer protocol. In standard
XModem, the transmitted blocks are 128 bytes.
1KB-XModem is an extension to XModem that
increases the block size to 1,024 bytes. Many newer
file-transfer protocols that are much faster and
more accurate than XModem have been developed,
such as YModem and ZModem.
XMS (extended memory specification) A
Microsoft-developed standard that provides a way
for real-mode applications to access extended mem-
ory in a controlled fashion. The XMS standard is
available from Microsoft.
XON/XOFF Standard ASCII control characters
used to tell an intelligent device to stop or resume
transmitting data. In most systems, pressing Ctrl+S
sends the XOFF character. Most devices understand
Ctrl+Q as XON; others interpret the pressing of any
key after Ctrl+S as XON.
Y-connector A Y-shaped splitter cable that
divides a source input into two output signals.
Y-mouse A family of adapters from P.I.
Engineering that enables a single mouse port to
drive two devices. P.I. Engineering also makes the Y-
see adapter for dual monitors and the Y-key adapter
for dual keyboards.
Yellow Book The standard used by CD-ROM.
Multimedia applications most commonly use the
Yellow Book standard, which specifies how digital
information is to be stored on the CD-ROM and
read by a computer. Extended architecture (XA) is
currently an extension of the Yellow Book that
enables the combination of various data types
(audio and video, for example) onto one track in a
CD-ROM. Without XA, a CD-ROM can access only
one data type at a time. Many CD-ROM drives are
now XA capable.
Yellow Book standards See CD-ROM.
YModem A file-transfer protocol first released as
part of Chuck Forsberg’s YAM (yet another modem)
program. An extension to XModem designed to
overcome some of the limitations of the original.
YModem enables information about the transmit-
ted file, such as the filename and length, to be sent
along with the file data and increases the size of a
Appendix A
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