24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 1 Appendix A Glossary This glossary contains computer and electronics terms that are applicable to the subject matter in this book. The glossary is meant to be as comprehensive as possible on the subject of upgrading and repairing PCs. Many terms correspond to the latest technology in disk interfaces, modems, video and display equipment, and standards that govern the PC industry.
4_0789736977_AppA.qxd 2 8/15/07 Appendix A 9:24 AM Page 2 Glossary 24x7 Refers to continuous 24 hours a day, 7 days a week computer or services operation. 802.11 The family name for various wireless Ethernet standards. See also IEEE 802.11 family. 56K The generic term for modems that can receive data at a maximum rate of 56Kbps. See also V.90, V.92, X2, K56flex. 1000BASE-T A 1,000Mbps Ethernet local area network (LAN) that runs over four pairs of Category 5 cable.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 3 Glossary Appendix A 3 80386DX An Intel microprocessor with 32-bit registers, a 32-bit data bus, and a 32-bit address bus. This processor can operate in real, protected virtual, and virtual real modes. lacks the built-in math coprocessor function and was designed as a low-cost version of the 486DX. The 486SX can operate in real, protected virtual, and virtual real modes.
24_0789736977_AppA.qxd 4 8/15/07 Appendix A 9:24 AM Page 4 Glossary access light The LED on the front of a drive or other device (or on the front panel of the system) that indicates the computer is reading or writing data on the device. access mechanism See actuator. access time The time that elapses from the instant information is requested to the point that delivery is completed. It’s usually described in nanoseconds (ns) for memory chips and in milliseconds (ms) for disk drives.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 5 Glossary wires to communicate digitally at high speed between the telephone company central office (CO) and the subscriber. ADSL sends information asymmetrically, meaning it is faster one way than the other. The original ADSL speed was T-1 (1.536Mbps) downstream from the carrier to the subscriber’s premises and 16Kbps upstream. However, ADSL is available in a variety of configurations and speeds. See also DSL.
24_0789736977_AppA.qxd 6 8/15/07 Appendix A 9:24 AM Page 6 Glossary answer mode A state in which the modem transmits at the predefined high frequency of the communications channel and receives at the low frequency. The transmit/receive frequencies are the reverse of the calling modem, which is in originate mode. See also originate mode. antialiasing Software adjustment to make diagonal or curved lines appear smooth and continuous in computer-generated images. See also aliasing.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 7 Glossary processing equipment. The standard ASCII character set consists of 128 decimal numbers ranging from 0 to 127, which are assigned to letters, numbers, punctuation marks, and the most common special characters. In 1981, IBM introduced the extended ASCII character set with the IBM PC, extending the code to 8 bits and adding characters from 128 to 255 to represent additional special mathematical, graphics, and foreign characters.
24_0789736977_AppA.qxd 8 8/15/07 Appendix A 9:24 AM Page 8 Glossary the Athlon XP is designed mainly for single processor applications. All three use the improved Thoroughbred core and 3DNow! Professional multimedia extensions. The Athlon XP processors include AMD’s new QuantiSpeed design for faster internal operation and are rated by their performances relative to the Intel Pentium 4, rather than by their clock speeds. For example, the Athlon XP 2600+, which performs comparably to the Pentium 4 2.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 9 Glossary available memory Memory currently not in use by the operating system, drivers, or applications, which can be used to load additional software. average access time The average time it takes a disk drive to begin reading any data placed anywhere on the drive.
24_0789736977_AppA.qxd 10 8/15/07 Appendix A 9:24 AM Page 10 Glossary bandwidth 1) Generally, the measure of the range of frequencies within a radiation band required to transmit a particular signal. The difference between the lowest and highest signal frequencies. The bandwidth of a computer monitor is a measure of the rate at which a monitor can handle information from the display adapter. The wider the bandwidth, the more information the monitor can carry and the greater the resolution.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 11 Glossary Appendix A 11 BBS (bulletin board system) A computer that operates with a program and a modem to enable other computers with modems to communicate with it, often on a round-the-clock basis. Although BBSs were once the primary means of distributing information and software, the Internet has almost completely replaced BBSs.
24_0789736977_AppA.qxd 12 8/15/07 Appendix A 9:24 AM Page 12 Glossary block diagram The logical structure or layout of a system in graphics form. Does not necessarily match the physical layout and does not specify all the components and their interconnections. Blu-ray Disc (BD) One of the two competing high-definition DVD format standards. Also see High Density Digital Versatile Disc (HD-DVD). Blue Book The standard for enhanced CDs (CD-E).
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 13 Glossary BRI Short for basic rate interface, it’s a form of ISDN used in home and small business applications. A 2B+1D BRI service has two B channels and a single D channel for signaling and control uses. bridge In local area networks, an interconnection between two similar networks. Also the hardware equipment used to establish such an interconnection. broadband transmission A term used to describe analog transmission.
24_0789736977_AppA.qxd 14 8/15/07 Appendix A 9:24 AM Page 14 Glossary busmaster An intelligent device that, when attached to the Micro Channel, EISA, VLB, or PCI bus, can bid for and gain control of the bus to perform its specific task without processor intervention. Most recent motherboards incorporate busmastering ATA/IDE host adapters, but this feature must be enabled in both the BIOS and through the installation of Windows drivers to be effective.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 15 Glossary swell and compress the median nerve, which carries impulses from the brain to the hand, causing numbness, weakness, tingling, and burning in the fingers and hands. Computer users get carpal tunnel syndrome primarily from improper keyboard ergonomics that result in undue strain on the wrist and hand. carrier A continuous frequency signal capable of being either modulated or impressed with another information-carrying signal.
24_0789736977_AppA.qxd 16 8/15/07 Appendix A 9:24 AM Page 16 Glossary mass production of multimedia applications. CD-R discs can be compatible with CD-ROM, CD-ROM XA, and CD audio. Orange Book specifies multisession capabilities, which enable data recording on the disc at various times in several recording sessions. Multisession capability enables data such as digital photos, digital music, or other types of data files to be added to a single disc on different occasions.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 17 Glossary resolution of 320×200 pixels in 16 colors or 640×200 pixels in two colors. The CGA outputs a TTL (digital) signal with a horizontal scanning frequency of 15.75KHz and supports TTL color or NTSC composite displays. channel 1) Any path along which signals can be sent. 2) In ISDN, data bandwidth is divided into two B-channels that bear data and one D-channel that carries information about the call.
24_0789736977_AppA.qxd 18 8/15/07 Appendix A 9:24 AM Page 18 Glossary clock multiplier A processor feature where the internal core runs at a higher speed than the motherboard or processor bus. See also overclocking. clock speed A measurement of the rate at which the clock signal for a device oscillates, usually expressed in millions of cycles per second (MHz).
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 19 Glossary collision In a LAN, if two computers transmit a packet of data at the same time on the network, the data can become garbled, which is known as a collision. collision detection/avoidance A process used on a LAN to prevent data packets from interfering with each other and to determine whether data packets have encountered a collision and initiate a resend of the affected packets. color graphics adapter See CGA.
24_0789736977_AppA.qxd 20 8/15/07 Appendix A 9:24 AM Page 20 Glossary computer-based training (CBT) The use of a computer to deliver instruction or training; also known as computer-aided (or assisted) instruction (CAI), computer-aided learning (CAL), computerbased instruction (CBI), and computer-based learning (CBL). A file that can be created to tell DOS how to configure itself when the machine starts up. It can load device drivers, set the number of DOS buffers, and so on. CONFIG.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 21 Glossary crash A malfunction that brings work to a halt. A system crash usually is caused by a software malfunction, and ordinarily you can restart the system by rebooting the machine. A head crash, however, entails physical damage to a disk and probable data loss. CRC (cyclic redundancy checking) An errordetection technique consisting of a cyclic algorithm performed on each block or frame of data by both sending and receiving modems.
24_0789736977_AppA.qxd 22 8/15/07 Appendix A 9:24 AM Page 22 Glossary Raw/2:1 compressed capacities for a single tape are 2/4GB for DDS, 4/8GB for DDS-2, 12/24GB for DDS-3, 20/40GB for DDS-4, and 36/72GB for DAT 72 (the latest standard). data 1) Groups of facts processed into information. A graphic or textural representation of facts, concepts, numbers, letters, symbols, or instructions used for communication or processing.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 23 Glossary DEBUG The name of a utility program included with DOS and used for specialized purposes, such as altering memory locations, tracing program execution, patching programs and disk sectors, and performing other low-level tasks. decibel (dB) A logarithmic measure of the ratio between two powers, voltages, currents, sound intensities, and so on. Signal-to-noise ratios are expressed in decibels.
_0789736977_AppA.qxd 24 8/15/07 Appendix A 9:24 AM Page 24 Glossary dialup adapter In Windows, a software program that uses a modem to emulate a network interface card for networking. Most commonly used to connect to an Internet service provider or a dialup server for remote access to a LAN. die An individual chip (processor, RAM, or other integrated circuit) cut from a finished silicon chip wafer and built into the physical package that connects it to the rest of the PC or a circuit board.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 25 Glossary and time of creation, and a pointer to the location of the file. Each entry in a directory is 32 bytes long. Windows refers to subdirectories (directories beneath the root directory) as folders. DirectX A set of graphics-related drivers and APIs that translates generic hardware commands into specific commands for particular pieces of hardware.
24_0789736977_AppA.qxd 26 DOCSIS 8/15/07 Appendix A 9:24 AM Page 26 Glossary See CableLabs Certified Cable Modem. doping Adding chemical impurities to silicon (which is naturally a nonconductor) to create a material with semiconductor properties that is then used in the manufacturing of electronic chips. DoS (denial of service) An Internet attack on a resource that prevents users from accessing email, websites, or other services. It usually exploits security shortcomings in email or web servers.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 27 Glossary dual-core processor A processor that contains two distinct physical processor cores in a single package. This type of processor provides most of the benefits of dual processor designs at a lower cost. dual independent bus (DIB) architecture A processor technology with the existence of two independent buses on the processor—the L2 cache bus and the processor-to-main memory system bus.
24_0789736977_AppA.qxd 28 8/15/07 Appendix A 9:24 AM Page 28 Glossary DVD+R/RW are the most compatible, fastest, most capable, and most popular of all the recordable DVD formats. See also DVD+R. DVD±RW A DVD drive capable of reading and writing to both DVD+R/RW and DVD-R/RW media. Some of these drives also support some or all of these media types: DVD+R DL, DVD-R DL, and DVD-RAM. DVI (Digital Video Interactive) A standard that was originally developed at RCA Laboratories and sold to Intel in 1988.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 29 Glossary a palette of 64) colors. The EGA outputs a TTL (digital) signal with a horizontal scanning frequency of 15.75KHz, 18.432KHz, or 21.85KHz, and it supports TTL color or TTL monochrome displays. EIA (Electronic Industries Association) An organization that defines electronic standards in the United States. EIDE (Enhanced Integrated Drive Electronics) A specific Western Digital implementation of the ATA-2 specification. See also ATA-2.
24_0789736977_AppA.qxd 30 8/15/07 Appendix A 9:24 AM Page 30 Glossary Energy Star A certification program started by the Environmental Protection Agency. Energy Star–certified computers and peripherals are designed to draw less than 30 watts of electrical energy from a standard 110-volt AC outlet during periods of inactivity. Also called Green PCs. See also E2000. Enhanced CD (CD-E) See Blue Book. enhanced graphics adapter See EGA. enhanced small device interface See ESDI. e-PCI-X The PICMG 1.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 31 Glossary extended partition A nonbootable DOS partition (also supported by Windows) containing DOS volumes. Starting with DOS v3.3, the FDISK program can create two partitions that serve DOS: an ordinary, bootable partition (called the primary partition) and an extended partition, which can contain as many as 23 volumes from D: to Z:. external device the system case.
24_0789736977_AppA.qxd 32 8/15/07 Appendix A 9:24 AM Page 32 Glossary file A collection of information kept somewhere other than in random-access memory. file attribute Information held in the attribute byte of a file’s directory entry. file compression See compressed file. filename The name given to the disk file. For DOS, it must be from one to eight characters long and can be followed by a filename extension, which can be from one to three characters long.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 33 Glossary FORMAT The DOS/Windows format program that performs both low- and high-level formatting on floppy disks but only high-level formatting on hard disks. formatted capacity The total number of bytes of data that can fit on a formatted disk. The unformatted capacity is higher because space is lost defining the boundaries between sectors. formatting Preparing a disk so the computer can read or write to it.
24_0789736977_AppA.qxd 34 8/15/07 Appendix A 9:24 AM Page 34 Glossary gender When describing connectors for PCs, connectors are described as male if they have pins or female if they have receptacles designed to accept the pins of a male connector. genlocking The process of aligning the data rate of a video image with that of a digital device to digitize the image and enter it into computer memory. The machine that performs this function is known as a genlock.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 35 Glossary dots. Newspapers, magazines, and many books use half-toning. The human eye merges the dots to give the impression of gray shades. handshaking The process of exchanging information about speeds and protocols between analog modems to establish a dialup connection. If your modem volume is high enough, you can hear handshaking as a series of distinct tones at the start of a modem-to-modem call.
24_0789736977_AppA.qxd 36 8/15/07 Appendix A 9:24 AM Page 36 Glossary from 655 to 2,125 scanning lines, having an aspect ratio of 5:3 (or 1.67:1) and a video bandwidth of 30MHz–50MHz (5+ times greater than the NTSC standard). Digital HDTV has a bandwidth of 300MHz. HDTV is subjectively comparable to 35mm film. High Definition Multimedia Interface (HDMI) A digital audio/video interface supporting uncompressed data on a single cable.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 37 Glossary 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.
24_0789736977_AppA.qxd 38 8/15/07 Appendix A 9:24 AM Page 38 Glossary Also refers to the ATA interface standard—the standard for attaching hard disk drives to ISA bus IBMcompatible computers. IDE drives typically operate as though they are standard ST-506/412 drives. See also ATA. IEEE 802.3 See 10BASE-2. IEEE 802.11 family A family of wireless network standards commonly known as wireless Ethernet, the most popular of which include 802.11a (54Mbps using 5GHz signaling), 802.11b (11Mbps using 2.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 39 Glossary interleaved memory The process of alternating access between two banks of memory to overlap accesses, thus speeding up data retrieval. Systems that require only one memory module per bank to operate can work more quickly when two are installed if the system supports interleaved memory. Inter-Module Bus (IMB) A proprietary highspeed bus used by the Broadcom ServerWorks chipsets. It runs at various speeds, depending on the chipset.
24_0789736977_AppA.qxd 40 8/15/07 Appendix A 9:24 AM Page 40 Glossary IRQ (interrupt request) Physical connections between external hardware devices and the interrupt controllers. When a device such as a floppy controller or a printer needs the attention of the CPU, an IRQ line is used to get the attention of the system to perform a task. On PC and XT IBMcompatible systems, eight IRQ lines are included, numbered IRQ0–IRQ7. On the AT and PS/2 systems, 16 IRQ lines are numbered IRQ0–IRQ15.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 41 Glossary Jaz drive A proprietary type of removable media drive with a magnetic hard disk platter in a rigid plastic case. Developed by Iomega, Jaz drives were discontinued in 2002, but media is still available for both 1GB and 2GB versions of the drive. JEDEC (Joint Electron Devices Engineering Council) A group that establishes standards for the electronics industry. JEDEC established the original PC66 SDRAM standard.
24_0789736977_AppA.qxd 42 8/15/07 Appendix A 9:24 AM Page 42 Glossary keylock Physical locking mechanism to prevent internal access to the system unit or peripherals. kibi A multiplier indicating 1,024 of some unit. Abbreviated as Ki. See also gibi. kilo A multiplier indicating one thousand (1,000) of some unit. Abbreviated as k or K. When used to indicate a number of bytes of memory storage, the multiplier definition changes to 1,024.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 43 Glossary LBA (logical block addressing) A method used with SCSI and IDE drives to translate the cylinder, head, and sector specifications of the drive to those usable by an enhanced BIOS. LBA is used with drives that are larger than 528MB and causes the BIOS to translate the drive’s logical parameters to those usable by the system BIOS.
24_0789736977_AppA.qxd 44 8/15/07 Appendix A 9:24 AM Page 44 Glossary drives, each with its own specifier. A primary partition can contain only one logical drive; an extended partition can contain one or more logical drives. See also extended partition and primary partition. logical unit number See LUN. lossless compression A compression technique that preserves all the original information in an image or other data structures.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 45 Glossary resistance to electricity changes in a material when brought into contact with a magnetic field (in this case, the read element material and the magnetic bit). Such drives use a magneto-resistive read sensor for reading and a standard inductive element for writing. A magneto-resistive read head is more sensitive to magnetic fields than inductive read heads.
24_0789736977_AppA.qxd 46 8/15/07 Appendix A Page 46 Glossary mean time between failure mean time to repair 9:24 AM See MTBF. See MTTR. MEB Stands for Mid-Level Electronics Bay, an SSI form factor originally developed for use with slotbased server processors, now used for four-way and larger designs. Sometimes erroneously referred to as EEB 3.5. mebi A multiplier indicating 1,048,576 of a unit of measurement.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 47 Glossary installations, the modem operates in dumb mode (no auto-dial capability), yet must go off-hook in originate mode to connect with answering modems. μ) A prefix indicating one millionth micro (μ (1/1,000,000 or .000001) of some unit. micron A unit of measurement equaling one millionth of a meter. Often used in measuring the size of circuits in chip manufacturing processes. Current state-of-the-art chip fabrication builds chips with 0.13 to 0.
24_0789736977_AppA.qxd 48 8/15/07 Appendix A 9:24 AM Page 48 Glossary adjusts to the fastest possible speed during connection. MNP Level 10EC is an improved version of MNP Level 10, adding more reliability and support for cellular phone hand-offs. MO (magneto-optical) MO drives use both magnetic and optical storage properties. MO technology is erasable and recordable, as opposed to CD-ROM (read-only) and WORM (write-once) drives. MO uses laser and magnetic field technology to record and erase data.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 49 Glossary specification defines the following minimum standard requirements: 25MHz 486SX with 4MB RAM, 160MB hard disk, 16-bit sound card,; 65,536-color video display, double-speed CD-ROM drive, and systems software compatible with the APIs of Microsoft Windows version 3.1 or later.
24_0789736977_AppA.qxd 50 8/15/07 Appendix A 9:24 AM Page 50 Glossary National Institute of Standards and Technology (NIST) A nonregulatory federal agency within the U.S. Commerce Department’s Technology Administration. Founded in 1901, NIST’s mission is to promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 51 Glossary CMOS NVRAM is used in IBM-compatible systems to store configuration information. True NVRAM often is used in intelligent modems to store a userdefined default configuration loaded into normal modem RAM at power-up. nonvolatile RAM disk A RAM disk powered by a battery supply so that it continues to hold its data during a power outage.
24_0789736977_AppA.qxd 52 8/15/07 Appendix A 9:24 AM Page 52 Glossary OLE (object linking and embedding) An enhancement to the original Dynamic Data Exchange (DDE) protocol that enables the user to embed or link data created in one application to a document created in another application and subsequently edit that data directly from the final document.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 53 Glossary overlay Part of a program loaded into memory only when it is required. overrun A situation in which data moves from one device more quickly than a second device can accept it. overscanning A technique used in consumer display products that extends the deflection of a CRT’s electron beam beyond the physical boundaries of the screen to ensure that images always fill the display area.
24_0789736977_AppA.qxd 54 8/15/07 Appendix A 9:24 AM Page 54 Glossary passive heatsink A heatsink that does not include a fan. Passive heatsinks used on processors are usually larger than active heatsinks and rely on case fans to dissipate heat. Many North Bridge or memory control hubs on recent motherboards also use passive heatsinks. passive matrix Another name for dual-scan, display-type LCDs.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 55 Glossary multimedia units have been improved by making the registers 128 bits wide and adding a separate register for data movement. Finally, SSE2 adds 144 new instructions for double-precision floatingpoint, SIMD integer, and memory management. The original Socket 423 version (Willamette) was later replaced by Socket 478 (Northwood) and finally by Socket 775 (Prescott) running at up to 3.6GHz. 800MHz system bus versions also support HT Technology.
24_0789736977_AppA.qxd 56 8/15/07 Appendix A 9:24 AM Page 56 Glossary thumbnails of each image on the disc are shown on the front of the case along with its index number. Multisession capability enables several rolls of film to be added to a single disc on different occasions. pin compatible Chips having the same pinout functions. For example, a VIA C3 processor is pin compatible with an Intel Celeron (Socket 370 version).
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 57 Glossary Appendix A 57 PLCC (plastic leaded-chip carrier) A chipcarrier package with J-leads around the perimeter of the package. proprietary bus on the rear of a portable computer, but so-called universal models might attach to the PC Card (PCMCIA) slot or to a USB port. Plug and Play (PnP) A hardware and software specification developed by Intel that enables a PnP system and PnP adapter cards to automatically configure themselves.
24_0789736977_AppA.qxd 58 8/15/07 Appendix A 9:24 AM Page 58 Glossary output has a PFC of 1.0. In practice, high-quality power supplies and UPS units have PFCs in the 90%–97% range (.90–.97 PFC). Programmable Logic Controller (PLC) An electronic device that can be programmed to control a process or machine operation.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 59 Glossary PUN (physical unit number) A term used to describe a device attached directly to the SCSI bus. Also known as a SCSI ID. As many as eight SCSI devices can be attached to a single SCSI bus, and each must have a unique PUN or ID assigned from 7 to 0. Normally, the SCSI host adapter is assigned the highest-priority ID, which is 7. A bootable hard disk is assigned an ID of 0, and other nonbootable drives are assigned higher priorities.
24_0789736977_AppA.qxd 60 8/15/07 Appendix A 9:24 AM Page 60 Glossary RDRAM (Rambus DRAM) A proprietary highspeed dynamic RAM technology developed by Rambus, Inc., which was supported by some 8xx series Intel chipsets for Pentium III and early Pentium 4 systems from 1999 through 2001. Memory modules with RDRAM chips are called RIMMs (Rambus inline memory modules). Rambus licenses its technology to other semiconductor companies, who manufacture the chips and RIMMs.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 61 Glossary REV A proprietary hard-disk-based removablemedia drive made by Iomega. REV has a native/ 2.6:1 compressed capacity of 35/90GB per cartridge. REV can be used for backup or primary storage. An autoloader is also available. See also autoloader. revolutions per minute (RPM) ment of rotational speed.
24_0789736977_AppA.qxd 62 8/15/07 Appendix A 9:24 AM Page 62 Glossary or DSL modem is an example of a simple router that connects the Internet to your own network. Many routers include firewall capability to block suspect packets from being transmitted between networks. scan lines The parallel lines across a video screen, along which the scanning spot travels in painting the video information that makes up a monitor picture. NTSC systems use 525 scan lines to a screen; PAL systems use 625.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 63 Glossary SEC (single edge contact) An Intel processor packaging design in which the processor and optional L2 cache chips are mounted on a small circuit board (much like an oversized memory SIMM), which might be sealed in a metal and plastic cartridge. The cartridge is then plugged into the motherboard through an edge connector called Slot 1 or Slot 2, which looks similar to an adapter card slot.
24_0789736977_AppA.qxd 64 8/15/07 Appendix A 9:24 AM Page 64 Glossary Server System Infrastructure (SSI) A series of power supply, motherboard, and chassis standards developed by Intel for servers. graphical shell and either COMMAND.COM (Windows 9x/Me) or CMD.EXE (Windows NT and later) as the command-line shell. ServerWorks A major developer of server chipsets for use with Pentium III Xeon and Xeon/Xeon MP processors. Now owned by Broadcom.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 65 Glossary SIP (single inline package) with only one row of leads. A DIP-like package Appendix A 65 snow A flurry of bright dots that can appear anywhere onscreen on a monitor. skinny dip Twenty-four-position and 28position DIP devices with .300" row-to-row centerlines. SO-J (small outline J-lead) A small DIP package with J-shaped leads for surface mounting or socketing.
24_0789736977_AppA.qxd 66 8/15/07 Appendix A 9:24 AM Page 66 Glossary Socket AM2 A 940-pin socket used by many versions of the AMD Athlon 64, 64 X2, 64 FX, Opteron, and Sempron processors. Socket F A 1207-pin socket used by AMD Quad FX platform processors to allow two dual-core processors to work together in a quad-core platform. Also called Socket 1207 FX by AMD and Socket L1 by NVIDIA. Socket T Early name for Socket 775. See also Socket 775.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 67 Glossary Stateful Packet Inspection (SPI) A technology used in firewalls to ensure that all incoming packets are the result of an outbound request. stepper motor actuator An assembly that moves disk drive read/write heads across platters by a sequence of small partial turns of a stepper motor. Once common on low-cost hard disk drives of 40MB or less, stepper motor actuators are now confined to floppy disk drives.
24_0789736977_AppA.qxd 68 8/15/07 Appendix A 9:24 AM Page 68 Glossary system files Files with the system attribute. Usually, the hidden files that are used to boot the operating system. The MS-DOS and Windows 9x system files include IO.SYS and MSDOS.SYS; the IBM DOS system files are IBMBIO.COM and IBMDOS.COM. System Management Mode (SMM) Circuitry integrated into Intel processors that operates independently to control the processor’s power use based on its activity level.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 69 Glossary control terminal mode and enable more complex operations, including file transmission and saving received files. terminator Hardware or circuits that must be attached to or enabled at both ends of an electrical bus. A terminator prevents the reflection or echoing of signals that reach the ends of the bus and ensures that the correct impedance load is placed on the driver circuits on the bus. Most commonly used with the SCSI bus and Thin Ethernet.
24_0789736977_AppA.qxd 70 8/15/07 Appendix A 9:24 AM Page 70 Glossary that controls the sequencing of the message components and regulates inbound traffic flow. See also OSI. transportable computer A computer system larger than a portable system and similar in size and shape to a portable sewing machine. Most transportables conform to a design similar to the original Compaq portable, with a built-in CRT display. These systems are characteristically very heavy and run on only AC power.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 71 Glossary Ultra DMA (UDMA or Ultra ATA) A protocol for transferring data to an ATA interface hard drive. The Ultra DMA/33 protocol transfers data in burst mode at a rate of 33MBps, whereas the even faster Ultra DMA/66 protocol transfers at 66MBps. Ultra DMA/66 also requires the use of a special 80-conductor cable for signal integrity. This cable also is recommended for Ultra DMA/33 and is backward compatible with standard ATA/IDE cables.
24_0789736977_AppA.qxd 72 8/15/07 Appendix A 9:24 AM Page 72 Glossary to answer V.21 calls from overseas. The actual transmission rate is 300 baud and employs frequency shift keying (FSK) modulation, which encodes a single bit per baud. V.22 An ITU standard for modem communications at 1,200bps, with an optional fallback to 600bps. V.22 is partially compatible with the Bell 212A standard observed in the U.S. and Canada.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 73 Glossary vacuum tube A device used to amplify or control electronic signals, it contains two major components: a cathode (a filament used to generate electrons) and an anode (a plate that captures electron current after it flows through one or more grids). Largely replaced by the transistor and integrated circuit in most small electronics applications, vacuum tubes in the form of CRTs are still used to make conventional monitors. See also CRT.
24_0789736977_AppA.qxd 74 8/15/07 Appendix A 9:24 AM Page 74 Glossary video adapter An expansion card or chipset built into a motherboard that provides the capability to display text and graphics onscreen. If the adapter is part of an expansion card, it also includes the physical connector for the monitor cable. If the chipset is on the motherboard, the video connector is on the motherboard as well. video graphics array See VGA.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 75 Glossary volume label An identifier or name of up to 11 characters that names a disk. VPN (virtual private network) A private network operated within a public network. To maintain privacy, VPNs use access control and encryption. VRAM (video random-access memory) VRAM chips are modified DRAMs on video boards that enable simultaneous access by the host system’s processor and the processor on the video board.
24_0789736977_AppA.qxd 76 8/15/07 Appendix A 9:24 AM Page 76 Glossary Wi-Fi Protected Access (WPA) A Wi-Fi Alliance standard designed to secure wireless networks, which is much more secure than the previous WEP standard. World Wide Web (WWW) Also called the Web. A graphical information system based on hypertext that enables a user to easily access documents located on the Internet. wide area network (WAN) A LAN that extends beyond the boundaries of a single building.
24_0789736977_AppA.qxd 8/15/07 9:24 AM Page 77 Glossary 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 designation) uses the Socket 603 or Socket 604. All Xeon processors have larger caches and memory addressing schemes than their desktop counterparts.
24_0789736977_AppA.qxd 78 8/15/07 Appendix A 9:24 AM Page 78 Glossary block from 128 bytes to 1,024 bytes. YModembatch adds the capability to transmit batches, or groups, of files without operator interruption. YModemG is a variation that sends the entire file before waiting for an acknowledgment. If the receiving side detects an error midstream, the transfer is aborted. YModemG is designed for use with modems that have built-in error-correcting capabilities.
