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Mechanism to Upgrade an OD-ROM Disk

IP.com Disclosure Number: IPCOM000105587D
Original Publication Date: 1993-Aug-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 114K

Publishing Venue

IBM

Related People

Kulakowski, JE: AUTHOR [+2]

Abstract

With the advent of OD-ROM technology, similar to CD-ROM, large amounts of data can be distributed at low cost. Data is stamped on an OD-ROM disk with the same organization as recorded data on a WORM (Write Once Read Many) disk or an MO (Magneto-Optic) disk. With only minor changes, an existing WORM or MO drive can be modified to include the OD-ROM reading capability. Although OD-ROM disks have less capacity than CD-ROM disks, the possibility of developing multi-function drives makes optical disk drives an attractive alternative to DASD devices since the user can amortize the cost of the drive over multiple applications.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 47% of the total text.

Mechanism to Upgrade an OD-ROM Disk

      With the advent of OD-ROM technology, similar to CD-ROM, large
amounts of data can be distributed at low cost.  Data is stamped on
an OD-ROM disk with the same organization as recorded data on a WORM
(Write Once Read Many) disk or an MO (Magneto-Optic) disk.  With only
minor changes, an existing WORM or MO drive can be modified to
include the OD-ROM reading capability.  Although OD-ROM disks have
less capacity than CD-ROM disks, the possibility of developing
multi-function drives makes optical disk drives an attractive
alternative to DASD devices since the user can amortize the cost of
the drive over multiple applications.

      When comparing OD-ROM technology to CD-ROM technology, an
OD-ROM technology has the capability of supporting improved access
times because of the track and sector addressing scheme.  The access
time is further improved by the use of constant angular velocity
recording since motor speed is a constant and does not have to vary
as function of track number address.  For CD-ROM, the motor RPM
changes as seeks are executed from the ID to the OD.

      Two potential applications for OD-ROM disk technology are low
cost distribution of manuals and software applications.  A
characteristic common to both manuals and software is that they are
revised quite frequently as problems are fixed and new function is
added.  OD-ROM disks, like CD-ROM disks, cannot be altered once
created.  This document describes a mechanism to allow text or
programs on an OD-ROM disk to be revised or altered through the use
of a low cost floppy disk containing the updates or by down loading
information over a teleprocessing network or LAN (Local Area
Network).

      Data are stored as a file on the OD-ROM disk in the same
fashion as a rewritable or WORM optical disk.  A Volume Table of
Contents (VTOC) is stored on the OD-ROM disk which defines the
location of files to allow access.  Knowing the starting address of a
file and an offset, data within a file can be accessed.  Typically a
host will analyze the VTOC area and request a portion of a file by
sending an LBA (Logical Block Address) and a Block Count to the
drive.  The LBA is the address of the first sector to be transferred
and the Block Count defines the total number of sectors to be
transferred.

      The application program normally does not have an awareness of
the relation of a request for data and the translation of this
request into a LBA to be read or written.  The application program
communicates the Input/Output request to the operating system and
relies on the host operating system to convert a request to read or
write data (which is normally specified in terms of an offset from
the beginning of the file and the number of bytes to be transferred)
into the units appropriate to the device (track and sector for a disk
drive and LBA for an optical device).  The operating system component
that performs this conve...