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Adaptive PDM Disclosure Number: IPCOM000127538D
Publication Date: 2005-Aug-31
Document File: 5 page(s) / 30K

Publishing Venue

The Prior Art Database


Here is the idea of the optimization of the best PDM number for each drive in order to relux areal density as much as possible. By this method, SER is boost up because of reluxed areal density without any yield loss which is related to PDM overflow.

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Adaptive PDM


Magnetic recording areal density can't be improved because recent technology has been almost matured. But to provide higher density HDD (Hard Disk Drive) is one of the most important factor in HDD business. So, all of HDD suppliers are working hard to improve SER (Soft Error Rate) at higher areal density. Since the component technology, like head and disk, is almost matured, other approaches from File Integration are expected to improve SER , for example, actual sector number reduction or real estate revisit.

Here, we invent new HDD test process which gives the appropriate sector numbers to each drive (adaptive PDM). This enable better SER without yield loss caused by PDM (Primary Defect Map ) overflow.

Current design

Total sectors in drives are categorized as data area, RDM (Reassign Defect Map ) area and PDM area. Sector number for PDM is assigned enough to prevent PDM overflow in MFG (Manufacturing) test. So, the drives which have small volume of PDM hold sectors which are not used for any purpose. Thus, to assign the fix number of PDM sectors, which is the current design, cause data format inefficiency .

The invention --- Adaptive PDM

Main idea of this invention is to reduce unused sectors as much as possible by making actual PDM equivalent to prepared PDM.This idea enables SER improvement by areal reduction. Sector number of PDM can be optimized by adaptive zone format. So, yield loss by PDM overflow will be minimized.

The following shows the procedure of spec definition of adaptive PDM including basic design and MFG test.

Basic design procedure.

Definition of PDM temporary Max value and total sector number

Consideration of yield impact and areal density relaxation

  Total sector number is automatically defined if PDM temporary Max value was fixed. Definition of default zone format

Areal density is refluxed because total sector number is reduced from current design.

SER should be equivalent among all zone.

Definition of optional zone format

Zone format definition in the condition of increased sector number in specific zones.

Channel related parameters is optimized as well as sector number.


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Discussion which zone have optional zone format The following parameters should be designed here.

How many zones have optional zone formats ?



Which zones have optional zone formats ?


  SER should be equivalent to current format design even if the zone format with largest number of sectors is applied. Merit of increasing optional zone format variations.

More significant Format efficiency Smaller SER valiance among all zone Demerit of increasing optional zone format variations.

More complicated MFG test

More time/effort for zone format tuning.

If PDM temporary Max value were assigned as zero, default areal density would be minimized. But MFG test would take more time and the process would be complicated since all drives need to be applied adaptive PDM.

Optional zone format is prepared at the stage of...