Bootable CD-ROM Format Specification

Offset Type Description

0 Byte Boot Indicator. 88 = Bootable, 00 = Not Bootable

1 Byte Boot media type. This specifies what media the boot image emulates in bits 0-32.

Bits 6 and 7 are specific to the type of system.

Bits 0-3 count as follows

0 No Emulation

1 1.2 meg diskette

2 1.44 meg diskette

3 2.88 meg diskette

4 Hard Disk (drive 80)

5-F Reserved, invalid at this time

bit 4 - Reserved, must be 0

bit 5 - Continuation Entry Follows

bit 6 - Image contains an ATAPI driver

bit 7 - Image contains SCSI drivers

2-3 Word Load Segment. This is the load segment for the initial boot image. If this value

is 0 the system will use the traditional segment of 7C0. If this value is non-zero

the system will use the specified segment. This applies to x86 architectures only.

For “flat” model architectures (such as Motorola) this is the address divided by

10.

4 Byte System Type. This must be a copy of byte 5 (System Type) from the Partition

Table found in the boot image.

5 Byte Unused, must be 0

6-7 Word Sector Count. This is the number of virtual/emulated sectors the system will

store at Load Segment during the initial boot procedure.

8-0B D Word Load RBA. This is the start address of the virtual disk. CD’s use

Relative/Logical block addressing.

0C Byte Selection criteria type. This defines a vendor unique format for bytes 0D-1F.

The following formats have currently been assigned:

0 - No selection criteria

1- Language and Version Information (IBM)

2-FF - Reserved

0D-1F Byte Vendor unique selection criteria.

Figure 5 - Section Entry

Offset Type Description

0 Byte Extension Indicator. Must be 44

1 Byte Bits 1-4 - Unused

5 - 1 = Extension Record follows, 0 = This is final Extension

6-7 - Unused