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Industry Standard Architecture (ISA)slots only allow peripheral components an intercon- nect that transfers information at a speed of 8MHz and are much less common than otherslots because they are used to connect older components.Peripheral Component Intercon- nect (PCI)is a much newer bus connection that was introduced in 1995 and is the most com- mon type of slot found in computers today;it can transfer information at a speed of 33MHzand can use direct memory access (DMA).DMA allows a peripheral the ability to bypass theCPU and talk directly with other peripheral components to enhance performance;you can con- figure eight DMA channels to allow this ability.Accelerated Graphics Port (AGP)is designedfor video card peripherals and allows a transfer speed of over 66MHz.It was not designed toreplace PCI,but to enhance video card operations and allow for faster access to system mem- ory for graphical functions.Figure 2-1 shows a mainboard with these slots. Chapter253UNDERSTANDING HARDWARE FIGURE 2-1Mainboard componentsOther peripherals might not have slots for peripherals on the mainboard;instead,they mightconnect via a cable to a port on the edge of the mainboard that is visible from the exterior ofthe computer (and,hence,difficult to see in Figure 2-1).These ports include the following: .PS/2 .COM (Serial) .LPT .USB .IEEE 1394 (FireWire) .PCMCIACMOSChipIDEcontroller slotsSIMMslotDIMMslotISAslotAGPslotProcessorslotPCIslot
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typical DVDs can read data over 16 times (16X) the speed of an audio CD.Most DVD andCD-ROM drives are connected to the main circuit boards in a computer via an AdvancedTechnology Attachment Packet Interface (ATAPI) that allows them to act like an IDE HDD. Typically,one of the four possible IDE devices in a computer is a DVD or CD-ROM driveand this drive must be configured using jumper switches on the DVD or CD-ROM driveitself in the same fashion as IDE hard disk drives. 52Chapter 2PREPARING FOR LINUX INSTALLATIONAlthough the data transfer rate of a DVD or CD-ROM drive is faster than that of afloppy or Zip drive, it is still slower than that of a HDD.If a DVD or CD-ROM drive isplaced on the same IDE channel as a HDD, it impacts and slows down the effectivedata transfer rate of the HDD;because of this, it is wise to place DVD and CD-ROMdrives on an IDE controller separate from any IDE HDDs. Many DVD and CD-ROM drives at the time of this writing can also write informationto DVD and CD-ROM discs respectively.These devices are called DVD-rewritable(DVD-RW) and compact disc-rewritable (CD-RW) drives. NOTEFlash memory drivesare a recent media type that use EEPROM chips to store information. They typically store more information than floppy disks and Zip disks,and some flash mem- ory drives can store more information than a CD-ROM.In addition,flash memory drives canbe plugged into the computer while the computer is on and can be removed in the same way; as a result,flash memory drives are quickly becoming a common medium for users who needto transfer files between computers. Mainboards and Peripheral ComponentsPrograms are loaded into physical memory and executed by the processor;however,some devicemust exist,that provides the interconnect between these hardware devices.This interconnect(also called a bus) is provided by a circuit board called the mainboardormotherboard.Thebus serves to connect common hardware components,such as the processor,physical memory, and disk drives,but also connects peripheral components,such as video cards,sound cards, andnetwork interface cards (NICs).Peripheral components commonly connect to the rest ofthe system by means of an Input-Output bus (also known as an I/O bus or expansion bus) thatis represented by different slots or ports on the mainboard itself;the three most common slotsfor peripheral devices include the following: .ISA .PCI .AGP
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Table 2-2 Example partitioning scheme for a primary master IDE HDD (Contunied) DescriptionLinux NameWindows NameFirst logical drive in the extended partition on the primary hda5G: master HDDSecond logical drive in the extended partition on the primary hda6H: master HDDThird logical drive in the extended partition on the primary hda7I: master HDDOther Information Storage DevicesIn addition to HDDs,other information stores are available,including floppy disks,Zip disks, DVDs and CD-ROMs.These are often referred to as removable mediabecause the mediumused to store the information is not fixed in the computer as with a HDD,but removable andtransferable between computers. Floppy disks store information electromagnetically like hard disks and are traditionally the mostcommon removable medium;it is referred to as floppy because the medium covered with fer- rous material used to store information is flexible (or floppy) in contrast to the rigid metalplatters used in HDDs.Floppy drives,also referred to as 31/2-inch floppy drives in reference tothe size of the removable storage unit,can hold much less data than HDDs (only 1.44MB) and have much slower data transfer rates. Zip disksare an evolution of floppy disks and although they look physically similar,they dif- fer from regular floppies in that they can hold considerably more information (up to 750MB). These sophisticated floppy disks cannot use regular 31/2-inch floppy disk drive units;they needto be used with special Zip drives,yet are commonly used to transport large files or makeback-up copies of important information in many homes and small offices. DVDs and CD-ROMs differ from all other disk media mentioned because they do not useferrous material and electromagnetic heads to store and retrieve data,but instead use lasers toread reflected light pulses.A pitted layer of reflective material,normally aluminum,is sand- wiched between layers of clear plastic and laser pulses are bounced off it.The pits in the sur- face deflect the laser pulses hitting them and the resulting pattern of disruption in reflectionof laser pulses is read as stored information.This technology gives DVDs and CD-ROMs someadvantages over other removable storage devices,including greater data transfer speed,largerstorage capacity,and more resistance to data loss.This makes them very useful in storing largeamounts of data,and as a result are the choice medium for distributing software such as theLinux operating system. DVD and CD-ROM drives are rated by the speed at which they can read data from the CD- ROM disc compared to the speed of a regular audio compact disc (CD);typical CD-ROMsat the time of this writing can read data over 50 times (50X) the speed of an audio CD,andChapter251UNDERSTANDING HARDWARE
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Unlike IDE,SCSI controllers are physically separate from the HDD and are usually attachedto the mainboard via slots on the mainboard itself.SCSI hard drives are able to transfer dataat much faster rates than IDE hard drives,and the SCSI controller card can interact withmore than one HDD at a time.However,IDE hard drives and controllers are less expensiveto manufacture than their SCSI counterparts and,thus,are the most common hard drive tech- nology in homes and small- to medium-sized business.For the purposes of this chapter,thediscussion is limited to IDE hard disks. Hard drives manufactured today can store over 160GB of data,and are often divided up intosmall,more manageable sections called partitions.Each partition must then be prepared tostore files.To do this,you must format each partition with a filesystemthat specifies how datashould reside on the hard disk itself. 50Chapter 2PREPARING FOR LINUX INSTALLATIONIn the Windows operating system, each drive letter (for example, C:, D:, E:) can cor- respond to a separate filesystem that resides on a partition on the hard drive. NOTEThere are limits to the number and type of partitions into which a HDD can be divided.Harddisk drives can contain a maximum of four major partitions (called primary partitions).Toovercome this limitation,you can optionally label one of these primary partitions as extended ; thisextended partitioncan then contain an unlimited number of smaller partitions calledlogical drives.Each logical drive within the extended partition and all other primary parti- tions can contain a filesystem and be used to store data.The table of all partition informationfor a certain hard disk is stored in the first readable sector outside all partitions called the Mas- ter Boot Record (MBR).Recall that a primary master IDE HDD is referred to as hda inLinux;the first primary partition on this drive is labeled hda1,the second hda2,and so on. Because there are only four primary partitions allowed on a hard disk,logical drives inside theextended partition are labeled hda5,hda6,and so on.An example of this partition strategy islisted in Table 2-2. Table 2-2 Example partitioning scheme for a primary master IDE HDDDescriptionLinux NameWindows NameFirst primary partition on the primary master HDDhda1C: Second primary partition on the primary master HDDhda2D: Third primary partition on the primary master HDDhda3E: Fourth primary partition on the primary master HDD hda4F: (EXTENDED)
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tion in a cost-effective manner on the disks they contain for later use.When information isneeded by the processor,it is transferred from the disk drive to RAM,such as when the oper- ating system starts during system startup or when application programs are executed on a run- ning system. Hard Disk DrivesTraditionally,most information was stored on magnetic tape by magnetic tape devices;this useof a magnetic medium was quickly transferred to the floppy drives and hard disk drives usedtoday.The process works similarly to the way audio and video tapes are recorded and playedback.A surface is covered with a ferrous material,and the constituent particles of this ferrousmaterial can be rearranged by electromagnetic heads to record data and can then be read bydetecting the pattern of arrangement using the same equipment.Unlike magnetic tape devices, which must fast-forward or rewind magnetic tape to read or write data,HDDs read and writeinformation to and from ferrous material coating rigid metal platters by spinning these plat- ters rapidly under articulated arms holding electromagnetic heads.HDDs are not directly wiredto the processor,but must pass through a hard disk controller card that controls the flow ofinformation to and from the HDD.These controller cards come in two general types:Inte- grated Drive Electronics (IDE)andSmall Computer Systems Interface (SCSI).Hard dri- ves that connect to these controllers must be of the same type;you must use IDE hard diskswith an IDE controller card and use SCSI hard disks with a SCSI controller card. IDE controllers,also known as Advanced Technology Attachment (ATA)controllers,are usu- ally circuit boards found on the bottom of an IDE hard drive and connect to the mainboardvia a ribbon cable.Most mainboards contain two slots for IDE ribbon cables (a primary con- troller slot and a secondary controller slot),and each IDE ribbon cable can have up to twoIDE hard drives attached to it;thus,most computers are limited to four IDE hard drives. Because each IDE ribbon cable can have two IDE hard drives attached to it,there must be amethod that can uniquely identify each IDE hard drive.This method involves setting jumperswitches on the physical IDE hard drive so that one IDE hard drive is called master and oneIDE hard drive is called slave on the same ribbon cable.Hence,the master hard drive con- nected to the primary IDE controller slot might be called a primary master IDE HDD. Table2-1 lists the four possible IDE hard drive configurations and their Linux names. Table 2-1 IDE HDD configurationsDescriptionLinux NamePrimary Master IDE HDDhdaPrimary Slave IDE HDDhdbSecondary Master IDE HDDhdcSecondary Slave IDE HDDhddChapter249UNDERSTANDING HARDWARE
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computer is powered down.SRAM is the type of physical memory used for Level 2 processorcaches and any memory chips attached directly to the main circuit boards of the computer. ROMRead-only memory (ROM) is physical memory that can be read but not written to,and isstored in a permanent,nonvolatile manner on integrated circuits (computer chips) inside thecomputer.Unlike RAM,this memory store is not reliant on the flow of electricity and remainsintact for an indefinite period on the computer in the absence of power.Due to this property, ROM is often used to store the initial programs used to initialize hardware components whenstarting a computer;and is known as BIOS (Basic Input/Output System) ROM.Althoughtrue ROMs are still in use,the fact that the information store in a ROM computer chip isimmutable leads to variants that are maintained in the absence of electrical flow,but can bealtered if need be.These ROM variants include the following: .Programmable read-only memory (PROM),which consists of a blank ROM com- puter chip that can be written to once and never rewritten again. .Erasable programmable read-only memory (EPROM),in which the informationcontents can be erased and rewritten repeatedly.The contents of EPROM must beerased and rewritten as a whole;individual parts cannot be singly modified.Anexample of EPROM memory is the complementary metal oxide semiconductor(CMOS)computer chip in a computer,which stores the configuration informationused by the BIOS ROM when the system is first powered on. .Electronically erasable programmable read-only memory (EEPROM)maintainsan information store that can not only be erased and rewritten as a whole,but canalso be modified singly,leaving other portions intact.This ability to store informa- tion statically in the absence of electricity yet modify it if needed is why EEPROMchips are popular in many peripheral computer components. 48Chapter 2PREPARING FOR LINUX INSTALLATIONThe type of memory used to store photographs in digital cameras is a type of EEP- ROM memory. NOTEDisk DrivesMost information in a computer is maintained using media that is nonvolatile and does notconsist of integrated circuits;the most common media of this type used today include harddisks,which are stored in hard disk drives(also referred to as hard drives or HDDs),com- pact disc read-only memory (CD-ROM)discs,which are inserted into CD-ROM disc dri- ves,and floppy disks,which are inserted into floppy disk drives.Disk drivedevices do nottransfer data as quickly as RAM or ROM,but can store vast amounts of modifiable informa-
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then work with the instructions in memory.The amount of RAM is directly related to com- puter performance because greater amounts of RAM memory allow more programs to runsimultaneously on the system.Different programs require different amounts of memory to exe- cute properly;thus,software programs,including operating systems,specify a minimumamount of RAM in their documentation.A Linux machine running the GNOME desktopGUI environment requires more memory than a Linux machine that does not use any GUIenvironments. RAM is classified into two major types:dynamic RAM (DRAM) and static RAM (SRAM). Dynamic RAM (DRAM)is the cheaper of the two types and,thus,is the most common.Ithas a slower access speed compared to SRAM and the information store it holds must berefreshed thousands of times per second,necessitating a continuous,uninterrupted flow of elec- tricity.If the flow of electricity to the DRAM chip is disrupted even for the briefest ofmoments,the information store is lost.DRAM is the type of physical memory commonlyreferred to simply as computer memory and is seen as an array of integrated circuits (chips) arranged on a small board called a stick,which in turn is connected into the computer s maincircuit board via slots.The number of transistors making up the chips on a stick of DRAMdetermines the amount of information that can be stored measured in megabytes (MB). Two different sticks of DRAM can have the same physical dimensions,but could hold vastlydifferent amounts of information.Three main types of DRAM sticks are available:singleinline memory modules (SIMM),dual inline memory modules (DIMM),and small out- line dual inline memory modules (SODIMM).SIMMs are the older of the two and connecttheir arrays of integrated circuits to the motherboard via a connection having connectors (pins) normally along only one edge;SIMMs are no longer produced and are not commonly seentoday.DIMMS are widely used today and connect their arrays of integrated circuits to themotherboard via a connection having connectors (pins) along both edges;having more con- nections,DIMMs are able to store more information and transfer it more rapidly thanSIMMs.SODIMMs are a physically smaller DIMM that is used in portable notebook com- puters and Macintosh systems. As technology changes,so does the nature of DRAM and the speed at which it works.Threerecent DIMM technologies include Synchronous Dynamic Random Access Memory(SDRAM),Double Data Rate Synchronous Dynamic Random Access Memory (DDRSDRAM),and Rambus Dynamic Random Access Memory (RDRAM).SDRAM uses thestandard DIMM connector on the motherboard and transfers data to and from the store onthe memory module in bursts and at a higher speed than traditional DRAM.DDR SDRAMis an enhanced SDRAM that is used on newer computers to increase speed.RDRAM is aproprietary product that uses a RIMM connection,which is a DIMM with different pin set- tings,and runs at a very high clock speed,thus transferring data at a rapid rate.RIMM is notan acronym,but a trademarked word of the Rambus Corporation. The second major type of RAM,static RAM (SRAM),is more expensive to produce andallows faster access time to stored information because the information store does not needconstant refreshing and can go for short periods without a flow of electricity.Nonetheless, this interruption in electrical flow must be brief,and the information store is lost when theChapter247UNDERSTANDING HARDWARE
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is comparable to a 16-bit processor running at 350MHz.Processors today typically work with32 or 64 bits of information at a time;most Intel processors available today,such as the Pen- tium Processor series,are 32-bit processors and are much less expensive than their 64-bitcounterparts,such as the Intel Itanium,SPARC,and Alpha processors. In addition to the number of bits a processor can handle at one time,a computer s cache sizeand location also affect a processor s ability to calculate larger volumes of data.A cacheis atemporary store of information;processors can use cache to store recently used instruction setsor information for future use.The more information a processor can store on its local circuitboard in a processor cache,the faster it can execute repetitive or frequently used instructionsets.A cache stored in the processor itself is referred to as Level 1 (L1) cache.Not all proces- sors have Level 1 caches,and if they do,they are not necessarily the same size.In place of,orin addition to,Level 1 cache,processors can utilize Level 2 (L2)cache,which is informationstored for retrieval in a separate computer chip that is connected to the processor via a high- speed link.Although not as fast as Level 1 cache,Level 2 cache is a much less expensive alter- native and is more common.Newer processors usually incorporate Level 2 cache into theprocessor itself;in this case,another cache called Level 3 (L3)cacheis added on a separatecomputer chip connected to the processor.Level 3 cache functions similarly to the Level 2cache found in older computers. In a situation that requires more processing ability than can be provided by a single processor, you might choose to add more than one processor to the system.Multiple processors can thenwork together to distribute the load and perform the same tasks faster;however,multiproces- sor support must be incorporated into the Linux kernel during installation.The most commonkernel configuration for using multiple processors is called symmetric multiprocessing (SMP) and allows the same operating system and memory use of both processors simultaneously forany task.Another configuration called asymmetric multiprocessing (ASMP)refers to a sys- tem in which each processor is given a certain role or set of tasks to complete independentlyof the other processors. Physical MemoryPhysical memoryis a storage area for information that is directly wired through circuit boardsto the processor.Physical memory is divided into two major categories:random access mem- ory (RAM)andread-only memory (ROM).Both RAM and ROM are stored on computerchips and allow access to information;however,RAM requires a constant supply of electricityto maintain stored information,whereas ROM is static in nature and is able to store informa- tion even when there is no power to the system.Following this,RAM is referred to as volatilememory because its contents are lost when you turn the computer off,whereas ROM is labeledas nonvolatile memory. RAMAs discussed in Chapter 1,software programs are files that contain instructions to be executedby the processor and are loaded into RAM physical memory upon execution;the processor can46Chapter 2PREPARING FOR LINUX INSTALLATION
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categories of processor architectures are Complex Instruction Set Computers (CISC)proces- sors and Reduced Instruction Set Computers (RISC) processors.CISC processors normallyexecute more complex individual commands than RISC processors;however,because complexcommands take longer to execute on a processor,RISC processors tend to be faster than CISCprocessors.The discussion is limited to the Intel processor architecture throughout the remain- der of this book because Intel is the most common CISC processor available in homes andbusinesses around the world. Chapter245UNDERSTANDING HARDWAREThe new Itanium processor from Intel is a RISC processor that has some CISC fea- tures.Because it differs in design from most RISC processors, its architecture is oftencalled the Explicitly Parallel Instruction Computing (EPIC)architecture. NOTEThe speed at which a processor can execute commands is related to an internal time cyclereferred to as clock speed.Similar to the way a quartz watch keeps time,the processor has acrystal that oscillates at a determinable frequency when current is passed though it.This is thedrumbeat to which the processor keeps time and by which all actions are measured.The clockspeed is measured in MegaHertz (MHz),or millions of cycles per second;a processor runningat 200MHz has a clock speed or oscillation frequency of 200 million cycles per second.Aprocessor might require one cycle to complete a command or might be superscalar,that is,ableto complete more than one command in any given cycle.In either case,the faster the clockspeed of the processor,the greater the number of commands it can execute in a given span oftime. The clock speed of the processor in a computer is separate from and does not needto match the clock speed of other hardware components in the computer;in mostcases, the clock speed of the processor is the fastest of any hardware componentinside the computer. NOTEClock speed alone is not the sole determination of the speed at which a processor can work. The amount of information a processor can work with or process at any given time,measuredin binary digits (bits),is also a major factor. Hence,processors are also classified by how much information they can work with at a giventime;the more information that can be moved or worked on at once,the faster data can bemanipulated.A computer able to process 16 bits of information at a time is over twice as fastas one that can process 8 bits of information at a time;an 8-bit processor running at 800MHz
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Acomputer is composed of hardware,which is simply a collection of switches and circuitsthat require operating system software to function in a meaningful way.This chapter intro- duces you to the hardware and software terminology necessary to install a Linux system anddiscusses how to obtain this information from several sources. Understanding HardwareFundamental to the installation of Linux is an understanding of the computer s various hard- ware components.This allows the user the ability to verify that any hardware detected auto- matically during installation was detected correctly and that the hardware meets any installationrequirements.The hardware components necessary to understand prior to installing Linuxinclude the following: .Central processing units (CPUs) .Physical memory .Disk drives .Mainboards and peripheral components .Video adapter cards .Keyboards and miceCentral Processing Units (CPUs) The core component of any computer is the central processing unit (CPU),also known as themicroprocessor or processor;it is where the vast majority of all calculations and processing ofinformation takes place.Processors are integrated circuit boards consisting of millions of tran- sistors forming electrical pathways through which electricity is channeled.They consist of twomain components:the Arithmetic Logic Unit (ALU)and the Control Unit (CU).The ALUis where all the mathematical calculations and logic-based operations are executed.The CU iswhere instruction code or commands are loaded and carried out,and often sends informationto the Arithmetic Logic Unit for execution. Processors can have their integral electronics arranged in different ways;this is referred to asthe processor s architectureor platform.Recall from Chapter 1, Introduction to Linux, thatthe Linux operating system is available for many different platforms,including SPARC (Scal- able Processor Architecture),Alpha,and Intel.These different arrangements of electrical cir- cuits can have a specific effect on the processor s speed of executing certain types of instructions. Hence,processors are categorized based on the types of instructions they execute.The two main
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