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GLOSSARY
T
THIN-FILM MEDIA
Seeplatedthinfilmmedia.
TRACK
Onesurfaceofacylinder.Apathwhichcontainsreproducibleinformationleftona magneticmediumbyrecordingmeansenergizedfromasinglechannel.
TRACK-FOLLOWING SERVO
TRACKS PER INCH (TPI)
Ameasurementofradialdensity.Tracksperinchofdiskradius.
TRACK POSITIONING
Themethod,bothmechanicalandelectrical,usedtopositiontheheadsoverthecorrect cylinderinadiskdrivesystem.
U
AnerrorthatisnotabletobeovercomewithErrorDetectionandCorrection.
UNFORMATTED CAPACITY
Storagecapacityofdiskdrivepriortoformatting;alsocalledthegrosscapacity.(See format.)Therawcapacityofadrivenottakingintoaccountthecapacitylossdueto storageoftheformatcontrolinformationonthedisksurfaces.
UNRECOVERABLE ERROR
AreaderrorfallingoutsidethecapabilityofanECCmechanismtocorrect,ornot abletobeovercomebyrereadingthedatainquestion,withorwithoutrepositioning thehead.
V
VOICE COIL MOTOR
Apositioningmotorthatusesthesameprincipleasavoicecoilinaloudspeaker.The motorhasnodetentpositions.Themechanicalmotionoutputofitcanbeeitherrotary orlinear.
W
WHITNEY HEAD
AsuccessortotheoriginalWinchesterread/writeheaddesign.Theprimarychange wastomaketheflexuresmallerandmorerigid.FirstusedinIBM3370/3380.
WHITNEY TECHNOLOGY
Amethodofconstructingaread/writeheadinarigiddiskdriveusingaWhitney head.InallotherdetailsitisthesameasWinchestertechnology.
WINCHESTER HEAD
WINCHESTER TECHNOLOGY
AmethodofconstructingarigiddiskdriveusingconceptsintroducedintheIBM model3340diskdrive.Theprimarychangesfrompriortechnologywastolowerthe massoftheslider,useofamonolithicslider,radicallychangingthedesignofthe flexureandhavingtheslidercometorestonalubricateddisksurfacewhendisk rotationceases.Inadditiontotheabove,atotallysealedchambercontainingtheread/ writeheadsanddiskswasusedtoprotectagainstcontamination.
WINDOW MARGIN
Theamountoftolerancearead/writesystemhasfortransitionjitterataspecifiederror ratelevel.
WORD
Anumberofbits,typicallyamultipleofeight,processedinparallel(inasingle operation).Standardwordlengthsare8,16,32and64bits(1,2,4,or8bytes).
WRITE
Therecordingoffluxreversalsonamagneticmedia.
WRITE
Theintentionaltimeshiftingofwritedatatooffsettheeffectsofbitshiftinmagnetic recording.
WRITE GATE SIGNAL
Adigitalinputsignallevelwhichcausesthedrivecircuitrytorecord(write)data.
GL – 6