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Adaptive Stress to Map a Defect

IP.com Disclosure Number: IPCOM000015771D
Original Publication Date: 2002-Mar-14
Included in the Prior Art Database: 2003-Jun-21
Document File: 1 page(s) / 38K

Publishing Venue

IBM

Abstract

Disclosed is a method to map a defect properly in Hard Disk Drive (HDD) when manufacturing. To detect a defect on a disk efficiently in short time, it is used a special read operation with some stresses. These stresses are data pattern frequency (without a randomizer), restricted ECC, disabled amplitude gain control, restricted decoding and so on. As a result, a repeated error sector is mapped as a defect.

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Adaptive Stress to Map a Defect

Disclosed is a method to map a defect properly in Hard Disk Drive (HDD) when manufacturing. To detect a defect on a disk efficiently in short time, it is used a special read operation with some stresses. These stresses are data pattern frequency (without a randomizer), restricted ECC, disabled amplitude gain control, restricted decoding and so on. As a result, a repeated error sector is mapped as a defect.

However there is different sensitivity to the stress between reading heads. Then that makes different defect detectability by the heads. Therefore it is able to minimize defect escape and too much detection by adapting those stresses to each head characteristic. Because the adaptive stress can uniform the defect detectability.

<Example1: Adaptive Data Pattern Frequency to Resolution> For each head,
1. Measure head amplitude using the fastest cyclic pattern and the slowest cyclic pattern.
2. Calculate the resolution of the head amplitude.
3. Determine the data pattern frequency by the resolution.

The resolution is low -> lower frequency is used.

The resolution is high -> higher frequency is used.
4. Perform the special read operation using the above data pattern to map a defect.

<Example2: Adaptive ECC length to Soft Error Rate> For each head,
1. Measure Soft Error Rate (SER) in one track.
2. Determine the ECC length by SER.

The SER is low -> Smaller ECC length is used.

The SER is high -> Larger ECC length is used.
4. Perform the speci...