CD/DVD Format, Boot Volume Descriptor | Western Digital T13/2132-D

June 23, 2010

T13/2132-D Revision 3

that supports CHS is acceptable (e.g., FAT-16 or FAT-32) The partition table shall only have one partition defined.

7.3 CD/DVD Format

7.3.1 Overview

The system BIOS can boot from a CD or DVD only if the format of the media has been predefined. ISO-9660 is a basic CD-ROM file system that has been incorporated into current CD and DVD file system standards. CD/DVD boot uses ISO 9660 as a framework to provide boot capability. ISO 9660 requires that a set of volume descriptors reside on the media starting at sector 10h. For data CD's, there will usually be a "Primary Volume Descriptor" at sector 10h followed by a "Set Terminator" at sector 11h. The "Primary Volume Descriptor" provides a pointer to the directory structures. ISO 9660 has also defined a "Boot Volume Descriptor" (BVD). BIOSes check the BVS to determine if a CD or DVD id bootable. A CD or DVD shall have a BVS at sector 11h on the media. The "Set Terminator" shall reside at sector 12h or higher. ISO 9660 requires that a "Set Terminator" be present. ISO 9660 formatting need not be present for a CD or DVD to be bootable. The only requirement is that a BVS be present at sector 11h.

7.3.2 Boot Volume Descriptor (BVD)

ISO 9660 does not define the payload for its BVD. This standard provides the necessary formatting to enable bootability. The BIOS shall check the data in the BVD to determine if boot is possible. Table 15 describes the BVD format.

		Table 15 — Boot Volume Descriptor

Offset	Type	Description
00h	Byte	Boot Record Indicator: this field shall be set to 00h

01h-05h	Byte	ISO-9660 specification identifier: this field shall be set to 43h 44h 30h 30h 31h
		("CD001")

06h	Byte	Descriptor Version: this field shall be set to 01h

07h-26h	Byte	This field shall be set to: 45h 4Ch 20h 54h 4Fh 52h 49h 54h 4Fh 20h 53h 50h 45h
		43h 49h 46h 49h 43h 41h 45h 49h 4Fh 4Eh 00h, 00h, 00h, 00h, 00h, 00h, 00h, 00h,
		00h ("EL TORITO SPECIFICATION" padded to the right with zeros).

27h-46h	Byte	Reserved

47h-4Ah	DWord	Absolute pointer to the first sector of the boot catalog

4Bh-7FFh	Byte	Reserved

Working Draft Enhanced Disk Drive - 4 (EDD-4)

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Western Digital T13/2132-D manual CD/DVD Format, Boot Volume Descriptor BVD

Contents

Revision June 23 Information technology Enhanced Disk Drive 4 EDD-4 Working Draft Enhanced Disk Drive 4 EDD-4 Points of ContactT13/2132-D Revision 3June 23 June 23 T13/2132-D Revision Draft T13/2132-D Revision June 23 American National Standard New Capabilities added to EDD-4 Document Status Contents Working Draft Enhanced Disk Drive 4 EDD-4 Vii Viii Working Draft Enhanced Disk Drive 4 EDD-4 Output Parameters Tables Figures Introduction Foreword Xii Working Draft Enhanced Disk Drive 4 EDD-4 American National Standard for Information Technology ScopeBSR Incits ATA8-APT ATA8-AST Approved Ansi References Name Normative references GeneralApproved references References Under Development Name Project Number References under developmentOther references June 23 T13/2132-D Revision Abbreviation Meaning Symbols and abbreviationsMaster Boot Record MBR The first LBA on a disk Conventions Ordered lists PrecedenceLists Lists overview Unordered lists Numbering T13/2132-D Revision June 23 Keywords Bit conventions Register and CF ContentsInterrupt Services and Functions Numbering conventions French English This standard QWord at word offset n ByteWord at offset n DWord at word offset n Byte Value ATA string byte swapping Word Byte Character in stringATA firmware revision example Word Overview Bit Description 8GB INT 13h Functions Conventional FunctionsConventional Register Definitions Register Description Conventional Function Definitions Function a Description Function Description 8GB INT 13h Functions OverviewData Structure Extended Function Definitions T13/2132-D Revision June 23 Device Address Packet Offset INT 13h Interface Subsets Fixed Disk Access SubsetFixed Disk Access Function Code Removable Media EDD Support Function Code Locking and Ejecting Function CodeEnhanced Disk Drive EDD Support Subset ISO 9660 CD Layout Working Draft Enhanced Disk Drive 4 EDD-4 CD/DVD Boot Overview System Area Unused Emulation Process Boot Methods Floppy Geometries Type Cylinders Heads Sectors No Emulation BootFloppy Boot Hard Drive Boot CD/DVD Format Boot Volume Descriptor BVDBoot Volume Descriptor Offset Type Description T13/2132-D Revision June 23 Validation Entry Section Header June 23 T13/2132-D Revision Initial/Default Entry 00h Byte Header ID Type Description June 23 T13/2132-D Revision Section Entry T13/2132-D Revision June 23 Section Entry Extension INT 13h Function Definitions Overview Reset Disk Subsystem FN 00h Get Status of Last Operation FN 01h Read Sectors into Memory FN 02h Write Sectors From Memory FN 03h Verify Sectors FN 04h Get Drive Parameters FN 08h Read Buffer FN 0Eh Write Buffer FN 0Fh Value Description Get Disk Type FN 15h Set Media Type FN 18h Park Heads FN 19h Identify Device Information FN 25h Interface Support Bit Map Description Check Extensions Present FN 41h Extended Read FN 42h Extended Write FN 43h Verify Sectors FN 44h Lock/Unlock Media FN 45h Eject Removable Media FN 46h Result Buffer Get Device Parameters FN 48h Ascii Interface Path Definitions part 1 Host Bus Type Offset T13/2132-D Revision June 23 Interface Path Device Path Definition 00h ATA Device 01h 02h..FFh Reserved Byte Word DWord QWord Byte Port number Device parameter table extension Offset 2-3 control port base Offset 5 Bios use only Bios use only Offset 6 IRQ numberOffset 7 READ/WRITE Multiple command block count Offset 0-1 I/O port base Offset 9 PIO type Offset 10-11 Bios selected hardware specific option flagsBit 7 32-bit transfer mode Bit 8 Atapi device uses command packet interrupt Bit 11 Ultra DMA Bit 13h 48-bit LBA addressing enabledJune 23 T13/2132-D Revision Bits 9-10 translation type Translation Type Bits Description Get Extended Media Change Status FN 49h Initiate Disk Emulation FN 4Ah Value Emulation Working Draft Enhanced Disk Drive 4 EDD-4 Terminate Disk Emulation FN 4Bh Initiate Disk Emulation & Boot FN 4Ch CD Command Packet Return Boot Catalog FN 4Dh Hardware Configuration Sub-Functions Set Hardware Configuration FN 4Eh Formatted Command Packet Offset Type Description Send Packet Command FN 50h Formatted Protocol Specific Data T13/2132-D Revision June 23 Output Parameters Security Protocol Commands FN 51h INT 15h Removable Media Eject Annex a Hybrid MBR boot Hybrid MBR boot overviewGPT support for hybrid MBR boot code Hybrid MBR boot code EAX Hybrid MBR boot code endeavor procedure Hybrid VBR boot code