Browse Prior Art Database

Method for Microcode Conversion of Logical Sector Addresses to Physical Sector Addresses

IP.com Disclosure Number: IPCOM000045804D
Original Publication Date: 1983-Apr-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Lowdermilk, DJ: AUTHOR

Abstract

Some types of hard disks are formatted, as part of their manufacturing procedure, with logical sector addresses written on the disk. In order to improve the performance of read or write operations when a track to track switch is to be performed, the logical sector addresses are offset from track to track. This is done to enable a controller reading a sector on one track to switch to an adjacent track and read the next sequential sector without the need of one or more intervening disk revolutions.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 80% of the total text.

Page 1 of 2

Method for Microcode Conversion of Logical Sector Addresses to Physical Sector Addresses

Some types of hard disks are formatted, as part of their manufacturing procedure, with logical sector addresses written on the disk. In order to improve the performance of read or write operations when a track to track switch is to be performed, the logical sector addresses are offset from track to track. This is done to enable a controller reading a sector on one track to switch to an adjacent track and read the next sequential sector without the need of one or more intervening disk revolutions.

Hardware controllers for this type of DASD (direct access storage device) are designed so that they work primarily with the logical addresses. Thus, before general read or write operations are initiated, the hardware is given the logical address of the sector at which it is supposed to begin the desired operation. Unfortunately, there are times when the logical disk address is or becomes unreadable. Thus, when a portion of the disk containing a logical address is "blown", when a logical address needs to be changed or when the disk needs to be reformatted, it will be necessary to read from or write on the disk using real addresses.

Because of hardware constraints, as noted above, a disk read or write must be performed using real addresses. In order to do this, an algorithm was developed to efficiently convert logical addresses to real addresses with the track to track sector offset co...