Browse Prior Art Database

Improved Method for Physically accessing Blocks on a Disk Drive

IP.com Disclosure Number: IPCOM000104644D
Original Publication Date: 1993-May-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Related People

Guttmann, JE: AUTHOR [+2]

Abstract

A method for physically accessing data blocks on a disk drive in a quick, efficient manner is disclosed.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 54% of the total text.

Improved Method for Physically accessing Blocks on a Disk Drive

      A method for physically accessing data blocks on a disk drive
in a quick, efficient manner is disclosed.

      Disk drives which use a "fixed block" architecture divide each
track on a disk's surface into multiple blocks.  Each block is
comprised of an identification (ID) field and a data field.
Electronic signals typically called "INDEX" and "SECTOR" define the
beginning of each block; "INDEX" also defines the beginning of the
track.  A pictorial representation of a disk drive track is shown in
Fig. 1.

      During normal operation, data is stored and retrieved from the
disk by accessing the blocks "logically" via the unique ID field
associated with each block.  There are times, however, when blocks
must be accessed "physically;" that is, the ID field is ignored and
data is transferred based on the physical location of the block on
the track.

      Fig. 2 shows a high level diagram of hardware logic capable of
quickly and efficiently handling both logical and physical block
accesses.  It incorporates the following features:

o   a register to capture block ID fields read from the disk;
o   a sector pulse counter;
o   a selector circuit;
o   a microprocessor-controlled bit for controlling the selector;
o   a microprocessor-programmed register which defines the expected
    ID field or sector number;
o   a comparator circuit.

      When a logical block access is de...