Bootable CD-ROM Format Specification

1.0 Overview

This specification defines how makers of CD-ROMs can package several "images" of floppy and hard disks on a

single CD with the ability to catalog these images and to selectively boot from any single image.

The possibility of booting a PC from a CD ROM has raised several possibilities, including:

1. Self-configuring CD-ROMs that manage their own resources, including operating systems and drivers

2. The embedding of multiple operating systems and drivers on the same CD-ROM for a variety of applications,

e.g., multi-language

3. The ability of the end user to select which operating system to boot

4. Copy protection for the CD ROM software and data

To accomplish this facility, there are currently two available technologies:

1. DOS-based drivers (e.g., SCSI or ATAPI)

2. The system BIOS.

Attempting to use DOS-based drivers (e.g., SCSI or ATAPI) to boot from a CD ROM creates a number of problems

such as resource conflicts and inordinate use of memory.

The BIOS, however, avoids these problems and offers other advantages, including:

1. Can boot from a variety of operating systems by accessing a Boot Catalog on the CD-ROM.

2. Offers the choice of configuring the CD ROM as a hard disk (C: or D:) or floppy (A:).

3. Renames existing drives when necessary.

4. Uses existing BIOS technology (Logical Block Access) to access code and data.

5. Compatible with all DOS and Windows applications using INT 13 functions.

Using the BIOS to boot from the CD ROM requires using the available system header on the CD ROM

1.1 Scope

This document describes in detail how to format a CD-ROM from which you can boot a suitably-equipped computer

system. It assumes you are familiar with standard BIOS INT 13 functions, ISO document number 9660,

IBM/Microsoft INT 13 Extensions Dated 9/92, Version 1.0 of the Enhanced Disk Drive Specification (authored by

Phoenix), and ATAPI..

1.2 Notation and Conventions

All numbers in this document are hexadecimal unless otherwise specified. All reserved or unused bytes are assumed to

be zero. All character strings are padded to their full length with hex zeros. All word, double word and quad word

values listed in this spec are in “Little Indian” (Intel) format.

1.3 Introduction

ATAPI-compliant IDE as well as SCSI CD-ROM drives can optionally provide new boot capabilities for personal

computer manufacturers and users. In the past IBM and compatible personal computers would first attempt to boot

from the floppy drive and if no floppy was present, from the hard disk.

This specification explains how the BIOS boot procedure can be enhanced to support a new medium, the CD-ROM.

The CD-ROM is a removable media type, much like a floppy, but with the capacity of a hard disk.