Specifications

Glossary
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hub A common connection point for multiple
devices in a network. A hub contains a number of
ports to connect several segments of a LAN
together. When a packet arrives at one of the ports
on the hub, it is copied to all the other ports so all
the segments of the LAN can see all the packets. A
hub can be passive, intelligent (allowing remote
management, including traffic monitoring and port
configuration), or switching. A switching hub is
also called a switch. See also switch.
Huffman coding A technique that minimizes
the average number of bytes required to represent
the characters in a text. Huffman coding works for
a given character distribution by assigning short
codes to frequently occurring characters and longer
codes to infrequently occurring characters.
hybrid fiber coaxial (HFC) A network (such as
that used by digital cable TV and two-way cable
modems) that uses fiber-optic cabling for its back-
bone with coaxial cable connections to each indi-
vidual computer or TV.
hyper-threading technology A method (also
called HT technology) developed by Intel for run-
ning two different instruction streams through a
processor at the same time. Introduced in 2002, HT
technology was first used in the Intel Xeon proces-
sor with hyper-threading technology, with speeds
starting at 2.8GHz; the first HT technology–enabled
desktop processor was the 3.06GHz Pentium 4.
hypertext A technology that enables quick and
easy navigation between and within large docu-
ments. Hypertext links are pointers to other sec-
tions within the same document, other documents,
or other resources, such as FTP sites, images, or
sounds.
HyperTransport AMD’s high-speed technology
for connecting the North Bridge and South
Bridge or equivalent chips on a motherboard.
HyperTransport runs at six times the speed of the
PCI bus (800MBps versus 133MBps for PCI). The
original name was Lightning Data Transport (LDT).
Several chipset makers, including AMD and
NVIDIA, use HyperTransport.
Hz An abbreviation for hertz—a frequency mea-
surement unit used internationally to indicate one
cycle per second.
i.Link Sony’s term for IEEE 1394/FireWire port.
See also FireWire.
I/O (input/output) A circuit path that enables
independent communication between the proces-
sor and external devices.
I/O controller hub See ICH.
I/O port (input/output port) Used to com-
municate to and from another device, such as a
printer or disk.
IA-64 Intel’s 64-bit processor architecture, first
used in the Itanium processor for servers.
IBMBIO.COM One of the DOS system files required
to boot the machine in older versions of PC-DOS
(IBM’s version of MS-DOS). The first file loaded
from disk during the boot, it contains extensions to
the ROM BIOS.
IBMDOS.COM One of the DOS system files required
to boot the machine in older versions of PC-DOS
(IBM’s version of MS-DOS). Contains the primary
DOS routines. Loaded by
IBMBIO.COM, it in turn
loads
COMMAND.COM.
IC (integrated circuit) A complete electronic
circuit contained on a single chip. It can consist of
only a few or thousands of transistors, capacitors,
diodes, or resistors, and it generally is classified
according to the complexity of the circuitry and
the approximate number of circuits on the chip. SSI
(small-scale integration) equals 2–10 circuits; MSI
(medium-scale integration) equals 10–100 circuits.
LSI (large-scale integration) equals 100–1,000 cir-
cuits, and VLSI (very-large-scale integration) equals
1,000–10,000 circuits. Finally, ULSI (ultra-large-scale
integration) equals more than 10,000 circuits.
ICH (I/O controller hub) Intel’s term for the
chip used in its 8xx chipsets to interface with
lower-speed devices such as PCI slots, USB ports,
ATA drives, and other devices traditionally con-
trolled by the South Bridge chip. ICH chips connect
with the memory controller hub (the 8xx chipsets’
replacement for the North Bridge) through a high-
speed hub interface. Current ICH chips used by
Intel 8xx–series chipsets include the ICH2 and
ICH4. See also MCH.
IDE (Integrated Drive Electronics) A hard
disk with the disk controller circuitry integrated
within it. The first IDE drives were called hard cards.
Appendix A
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