Samsung spinpoint v40, 3.5" hard disk drives manual Write Caching

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DISK DRIVE OPERATION

Thus Read Caching can provide substantial time savings during at least half of all disk requests. For example, Read Caching could save most of the disk transaction time by eliminating the seek and rotational latency delays that prominently dominate the typical disk transaction.

Read Caching operates by continuing to fill its cache memory with adjacent data after transferring data requested by the host. Unlike a non-caching controller, The SID2001 Interface Controller continues a read operation after the requested data has been transferred to the host system. This read operation terminates after a programmed amount of subsequent data has been read into the cache memory.

The cache memory consists of a 512KB sync DRAM buffer allocated to hold the data. It can be directly accessed by the host by means of read and write commands. The unit of data stored is the logical block, or a multiple of the 512-byte sector. Therefore, all accesses to cache memory must be in multiples of the sector size. The following commands empty the cache:

IDENTIFY DRIVE (ECh)

FORMAT TRACK (50h)

EXECUTE DRIVE DIAGNOSTIC (90h)

READ LONG (23h)

WRITE VERIFY (3Ch)

INITIALIZE DEVICE PARAMETER (91h)

SLEEP (99h, E6h)

STANDBY IMMEDIATELY (94h,E0h)

READ BUFFER (E4h)

WRITE BUFFER (E8h)

WRITE SAME (E9h)

5.5.2Write Caching

Write caching improves both single and multi-sector write performance by reducing delays introduced by rotational latency. When the drive writes a pattern of multiple sequential data, it stores the data to a cache buffer and immediately sends a COMMAND COMPLETE message to the host before it writes the data to the disk.

The data is then written collectively to the drive thereby minimizing the disk seeking operation. Data is held in cache no longer than the maximum seek time plus rotational latency. Host retries must be enabled for Write Caching to be active.

If the data request is random, the data of the previous command is written to the disk before COMMAND COMPLETE is posted for the current command. Read commands work similarly. The previous write is allowed to finish before the read operation starts.

If a defective sector is found during a write, the sector is automatically relocated before the write occurs. This ensures that cached data that already has been reported as written successfully gets written, even if an error should occur.

If the sector is not automatically relocated, the drive drops out of write caching and reports the error as an ID Not Found. If the write command is still active on the AT interface, the error is reported during that command. Otherwise, it is reported on the next command.

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SpinPoint V40 Product Manual

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Contents Spinpoint SpinPoint V40 Product Manual Table of Contents Smart Ervo S Ystem EAD and W Rite O PerationsIrmware F Eatures Timing Programming RequirementsProtocol Overview Maintenance Precautions Service and Repair107 General InformationTable of Figures Page Scope User DefinitionManual Organization Commands and Messages Terminology and ConventionsComputer Message Format C/SReference Description Key FeaturesIntroduction Standards and Regulations Hardware RequirementsSpecification Summary SpecificationsPhysical Specifications Logical ConfigurationsPerformance Specifications Power Requirements 28.71Environmental Specifications SV6003H SV6014H SV8004HReliability Specifications Mtbf POHInstallation Space RequirementsOrientation Unpacking InstructionsMounting 2Mounting Dimensions in Millimeters Clearance 3Mounting-Screw ClearanceCable Connectors DC Power ConnectorAT-Bus Interface Connector VentilationSpinPoint V40 Product Manual Jumper Block Configurations Options for Jumper Block Configuration Drive Installation 7DC Power Connector and AT-Bus Interface Cable ConnectionsSystem Startup Procedure ParameterSystem Setup Head / Disk Assembly HDA Base Casting AssemblyDC Spindle Motor Assembly Disk Drive OperationExploded Mechanical View Disk Stack Assembly Head Stack AssemblyVoice Coil Motor and Actuator Latch Assemblies Air Filtration SystemAT Disk Controller Digital Signal Process and Interface ControllerDrive Electronics 2SID2001 AT Controller Block Diagram Host Interface Control Block Buffer Control Block Disk Control BlockSpinPoint V40 Product Manual Power Management Read/Write ICDisk ECC Control Block Frequency SynthesizerTime Base Generator Automatic Gain ControlAsymmetry Correction Circuitry ASC Analog Anti-Aliasing Low Pass Filter3Read/Write 88C5200 Read Channel Servo SystemRead and Write Operations Read Caching Firmware FeaturesWrite Channel Write Caching Defect Management Automatic Defect AllocationMulti-burst ECC Correction SmartBlank Physical Interface Signal ConventionsSignal Summary Signal Descriptions DMACK- DMA Acknowledge Dmarq DMA RequestIntrq Drive Interrupt IOCS16- Drive 16-bit I/OIordy I/O Channel Ready PDIAG- Passed DiagnosticsRESET- Drive Reset SD8 SD6 SD9 SD5 SD4SD3 SD2Drive Drive HostDIR Logical Interface GeneralBit Conventions EnvironmentSpinPoint V40 Product Manual Command Block Registers 2 I/O Register AddressControl Block Registers N N N A a aControl Block Register Descriptions Alternate Status Register 3F6hDrive Address Register 3F7h Device Control Register 3F6hCommand Block Register Descriptions Features Register 1F1hError Register 1F1h Data Register 1F0hCommand Register 1F7h Sector Count Register 1F2hCylinder High Register 1F5h Cylinder Low Register 1F4hStatus Register 1F7h BSY Drdy DWF DSC DRQ Corr IDX ERRAt Command Register Descriptions Command Parameter Used SpinPoint V40 Product Manual Download Micro Code 92h Check Power Mode 98h, E5hExecute Device Diagnostics 90h Identify Device ECh Flush Cache E7hFormat Track 50h Word Content Description XxxxCapabilities Command set supported 95-128 0000h Reserved 129-159 Vendor specific 160-255 Initialize Device Parameters 91h Idle 97h,E3hIdle Immediate 95h,E1h Read Buffer E4h Read Long 22hwith retry, 23h without retryRead Multiple Command C4h Read Native Max Address F8h Read Sectors 20hwith retry, 21hwithout retrySeek 7xh Read Verify Sectors 40hwith retry, 41hwithout retryRecalibrate 1xh Set Features EFh ModeInputs LBANormal outputs BSY Drdy DRQ ERRDescription Set Multiple Mode C6h Sleep 99h, E6hSmart B0h Smart disable operation D9hStandby 96h,E2h Smart execute off-line immediate D4h Smart enable/disable attribute autosave D2hSmart enable operations D8h Smart read data D0h Byte DescriptionsValue Definition Off-line data collection capabilitySmart capability Smart read log sector D5hSmart return status DAh Smart save attribution value D3hStandby 96h, E2h Standby Immediate 94h, E0hWrite Buffer E8h Write DMA CAhWrite Multiple Command C5h Write Sectors 30hwith retry, 31hwithout retrySpinPoint V40 Product Manual Programming Requirements Reset ResponseError Posting Command Error Register Status Register BBKPower Conditions Sleep modeStandby mode Idle modeNormal mode PIO Data in Commands Protocol OverviewPIO Read Aborted Command PIO Data Out CommandsPIO Read Command PIO Write Command PIO Write Aborted CommandBSY=0 DRDY=1 BSY=1 BSY=0 DRQ=1 BSY=1 DRQ=0Non-Data Commands DMA Data Transfer Commands BSY=1 BSY=0 Aborted DMA Command Initialize DMA Reset DMA StatusBSY=0 BSY=1 Timing Register transfersDIOR-/DIOW Write PIO timing parameters Mode PIO data transfersAddr valid See note T1 t2 DIOR-/DIOW Multiword DMA data transfer DIOR-/DIOWMultiword DMA timing parameters Mode Ultra DMA data transfer Initiating an Ultra DMA data in burstUltra DMA data burst timing requirements 19Ultra DMA data burst timing requirementsSustained Ultra DMA data in burst 5Sustained Ultra DMA data in burstHost pausing an Ultra DMA data in burst 6Host pausing an Ultra DMA data in burstDevice terminating an Ultra DMA data in burst 7Device terminating an Ultra DMA data in burst 100Host terminating an Ultra DMA data in burst 8Host terminating an Ultra DMA data in burstInitiating an Ultra DMA data out burst 9Initiating an Ultra DMA data out burst 102Sustained Ultra DMA data out burst 10Sustained Ultra DMA data out burstDevice pausing an Ultra DMA data out burst 11Device pausing an Ultra DMA data out burst 104Host terminating an Ultra DMA data out burst 12Host terminating an Ultra DMA data out burstDevice terminating an Ultra DMA data out burst 13Device terminating an Ultra DMA data out burst 106General Information Maintenance PrecautionsService And Repair