Browse Prior Art Database

Disc File Controlled by Multiplexed Servo Samples

IP.com Disclosure Number: IPCOM000059606D
Original Publication Date: 1986-Jan-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Jones, I: AUTHOR

Abstract

In a multiple-head disc file, the actuator arm is controlled by a sampled servo system. Servo bursts are recorded on each track in positions that allow them to be read in sequence by switching between the heads. This reduces total space occupied by servo information and increases data recording space and format flexibility. The servo information assists the following tasks: a) Counting tracks crossed during arm motion (Seeks). b) Maintaining position on track while the arm is 'stationary' despite various deviations of the spindle and disk motion. c) Making adjustment to the mean track position to compensate for differences between heads. d) Giving a timing reference from which the approximate start of data can be recognized.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 72% of the total text.

Page 1 of 1

Disc File Controlled by Multiplexed Servo Samples

In a multiple-head disc file, the actuator arm is controlled by a sampled servo system. Servo bursts are recorded on each track in positions that allow them to be read in sequence by switching between the heads. This reduces total space occupied by servo information and increases data recording space and format flexibility. The servo information assists the following tasks: a) Counting tracks crossed during arm motion (Seeks). b) Maintaining position on track while the arm is 'stationary' despite various deviations of the spindle and disk motion. c) Making adjustment to the mean track position to compensate for differences between heads. d) Giving a timing reference from which the approximate start of data can be recognized. Existing types of servo include: 'Wedge' servos, with one sample per track (at index point) for task (c); dedicated servos, with a complete surface providing very well for tasks (a), (b) and (d), but relying on other compensation of head-to-head differences; and sector servos, with servo information on each track, between data sectors, for all four tasks. If it is arranged that the servo bursts on each track are staggered relative to each other, then servo samples can be obtained without the loss of data recording area inherent in both dedicated and sector servo designs. For example, if a disc file had 8 heads and 64 data sectors plus 64 servo bursts per track, adopting the present multiplexed...