Western-digital T13/2132-D User Manual download pdf (Page 35)

June 23, 2010 T13/2132-D Revision 3

Working Draft Enhanced Disk Drive - 4 (EDD-4) 23

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

1 2 ... 30 31 32 33 34 35 36 37 38 39 40 ... 85 86

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Western-digital T13/2132-D User Manual Page 35