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Browse Prior Art Database

Faster Track Centerline Acquisition After Seek for a Personal Computer Hardfile

IP.com Disclosure Number: IPCOM000062422D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Keener, DS: AUTHOR

Abstract

This article describes a technique to reduce the amount of time required to reach the track centerline in a computer hardfile if misregistration exists. Presently, some hardfiles do not have the capability to determine the magnitude of track misregistration. The only information available to the drive microprocessor is the direction of this misregistration. This information is conveyed to the microprocessor by a signal called "offtrack sense". The value of offtrack sense (1 or 0), which is sampled at index time, informs the drive whether the misregistration is inward or outward from the actual track centerline. In response to this signal, the drive microprocessor makes an incremental correction in the position of the heads to move them towards the true track centerline.

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Faster Track Centerline Acquisition After Seek for a Personal Computer Hardfile

This article describes a technique to reduce the amount of time required to reach the track centerline in a computer hardfile if misregistration exists. Presently, some hardfiles do not have the capability to determine the magnitude of track misregistration. The only information available to the drive microprocessor is the direction of this misregistration. This information is conveyed to the microprocessor by a signal called "offtrack sense". The value of offtrack sense (1 or 0), which is sampled at index time, informs the drive whether the misregistration is inward or outward from the actual track centerline. In response to this signal, the drive microprocessor makes an incremental correction in the position of the heads to move them towards the true track centerline. This incremental correction is fixed in value regardless of the magnitude of the misregistration. This correction is made once each revolution of the disk spindle, which is 16.67 ms. The magnitude of the incremental correction is approximately .75% of the track width. If the predicted track centerline was 5% of track width from the actual track centerline, then 5/.75 =
6.66 or seven revolutions are required to reach true track centerline. Refer to Fig. 1, which is a diagram of 5% offtrack after seek complete. The technique disclosed herein reduces the amount of time required to reach the track centerline if misregistration exists. The drive microprocessor has the ability to know if the data heads are positioned over the track centerline by detecting the offtrack...