Chapter 22You Will Learn…SCSI BasicsThe SCSI SubsystemThe SCSI SubsystemIDE vs. SCSI Bus CommunicationSlide 7Host AdaptersBIOSExpansion SlotBus MasteringSCAM-CompliantVendors for SCSI Host AdaptersSCSI Device DriversVariations in SCSIBus WidthSCSI Cables Signaling MethodsSingle-Ended SignalingDifferential SignalingSCSI CablesSignaling SymbolsSCSI Cable ConnectorsSCSI Cable ConnectorsTerminationWays to Terminate a SCSI ChainTypes of TerminatorsMajor Versions of SCSISCSI StandardsSCSI Cable SpecificationsComparing IDE and SCSISlide 31Slide 32Basic Steps for SCSI InstallationInstalling a Host Adapter CardSlide 35Installing a Host Adapter CardSetting Device IDs During InstallationSlide 38Setting External Device IDsSetting Internal Device IDsInstalling a SCSI Hard DriveGeneral Troubleshooting TipsTroubleshooting Installation ProblemsTroubleshooting Booting ProblemsChapter SummaryChapter 22All About SCSIYou Will Learn…About basics of SCSI (Small Computer System Interface) technology and componentsHow SCSI hard drives compare to IDE drivesHow to install a SCSI deviceTroubleshooting tips for SCSISCSI BasicsStandard for communication between subsystem of peripheral devices and system busBus can contain/be used by up to 7 or 15 devices, depending on SCSI standardBus controller can be either:•An expansion card (host adapter)•Embedded on motherboardThe SCSI SubsystemHost adapter• Gateway from the SCSI bus to the system bus• Card inserted onto expansion slot on mother board• Manages all devices on SCSI bus•Supports internal and external SCSI devices•Forms a single daisy chain with devicesTwo devices on SCSI bus can pass data between them without going through CPU; convenient for back upThe SCSI SubsystemIDE vs. SCSI Bus CommunicationThe SCSI SubsystemSCSI drive has its controller mounted inside the drive housing and can have a variable number of sectors per trackEach end of the SCSI chain has a terminating resistorEach device on the bus is assigned a SCSI IDTwo important components• Host adapters• Device driversHost AdaptersIssues to consider when selecting a host adapter•BIOS•Expansion slot•Bus masteringBIOSLook for a host adapter that is PnP compatible and has a configuration utility built into its ROMCheck for software that configures termination and assigns system resourcesLook for a host adapter whose BIOS can configure SCSI devices using the bus controlled by the adapterSee how many devices the BIOS supports (up to 15 is best)Expansion SlotHost adapter must fit the expansion slot you plan to useChoose 32-bit PCI bus for faster data transfer rate (Pentium motherboard)Bus MasteringChoose a host adapter that supports bus mastering, if your system bus supports itSCAM-CompliantSCAM = SCSI Configuration AutoMaticallyMethod by which SCSI devices and the host adapter can be PnP compliantTwo levels (Level 1 and Level2)Vendors for SCSI Host AdaptersSCSI Device DriversEnable OS to communicate with a host adapterTwo popular driver types•ASPI (Advanced SCSI Programming Interface) – more popular of the two•CAM (Common Access Method)Variations in SCSIStandardsTypes of cablingBus widthsBus WidthNarrow SCSI (8 bits)Wide SCSI (16 bits)SCSI Cables Signaling MethodsSingle-Ended SignalingSend a signal on a pair of twisted wires; one carries voltage, the other is a groundLess expensive, but maximum cable length cannot be as long because data integrity is not as greatDifferential SignalingSend a signal on a pair of twisted wires; both carry voltage, and the signal is calculated to be the difference between the two voltagesBetter signal accuracyGreater reliability and reduction in chance of data errorsHigh Voltage Differential (HVD)Low Voltage Differential (LVD)SCSI CablesSignaling SymbolsSCSI Cable ConnectorsSCSI Cable ConnectorsTerminationProvides an echo effect from electrical noise and reflected data at the end of the SCSI daisy chainWays to Terminate a SCSI ChainHost adapter can have a switch setting that activates or deactivates a terminating resistor on the cardDevice can have either a single SCSI connection or two connections (external terminator)Device at end of the chain can be terminated by a resistor physically mounted on that deviceInternal terminatorControlled by softwareTypes of TerminatorsPassive terminatorsActive terminatorsForced perfect terminators (FPTs)Major Versions of SCSISCSI-1 = Regular SCSI•8-bit data bus• 7 possible devicesSCSI-2 = Fast SCSI• Common command set• 16-bit data bus• 15 possible devices•Mandatory parity checkingSCSI-3 = Ultra SCSI•Supports both parallel and serial data transmission• Supports FireWire connections• Data transfer of 320 MB/sec•SPI (SCSI Parallel Interface) standardsSCSI StandardsSCSI Cable SpecificationsComparing IDE and SCSIIDE supports only four internal devices; SCSI supports both internal and external and allows you to add moreSCSI devices are generally of higher quality than IDE devices and more expensiveIDE devices require separate IRQ for each device; SCSI requires only one for entire chaincontinu ed …Comparing IDE and SCSIBoth are generally backward-compatibleSCSI hard drive with supporting host adapter and cable costs more than an IDE hard driveSCSI subsystem provides faster data transfer than an IDE driveSCSI generally provides better performance than IDE; often used on high-demand serverscontinu ed …Comparing IDE and SCSIGood host SCSI host adapter allows connection of other SCSI devices to itWith SCSI, two or more devices can operate simultaneously; with IDE, only one IDE drive on an IDE channel can be busy at a timeBasic Steps for SCSI Installation1. Set jumpers or switches on host adapter and install it on motherboard; install host adapter drivers2. Use jumpers or switches to assign SCSI ID3. Attach cabling to host adapter and each device4. Verify termination at both ends of daisy chain5. Power up one device at a time6. Install drivers and softwareInstalling a Host Adapter CardInstall card in expansion slotChange/verify default settings using setup programVerify settings under Advanced Configuration OptionsWindows supports host adapter; it loads device drivers automatically and installs host adapterUse Device Manager to verify correct installation of host adapterInstall external SCSI