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[这个贴子最后由欢畅在 2001/09/29 06:04pm 编辑]

How does a PC boot from CD-Rom?
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A PC can boot from a CD-Rom if the PCs BIOS supports the El Torito Bootable CD-ROM Format Specification v1.0.
This specification provides a way of getting to the location on the CD that will provide the boot information, while maintaining ISO-9660 compatibility.
The El Torito specification was created in january 1995, by Curtus E. Stevens (Phoenix) and Stan Merkin (back then IBM). And it was called after a restaurant, the "El Torito grill", where they went to eat and talk about bootable CD-Roms。
The ISO-9660 defines that a "Primary Volume Descriptor" must reside at sector 10h (16 decimal), relative to the start of the session, followed by any number of other Volume Descriptors, ended by a "Volume Descriptor Set Terminator".
The El Torito specification builds on this format by using a Boot Record Volume Descriptor as defined in section 8.2 of ISO-9660. This Boot Record must be located at sector 11h (17 decimal) in the last session of the CD.
The boot record contains an absolute pointer to the boot catalog. This catalog allows the system to pick a proper boot image to boot from.
Boot Record Volume Descriptor
Offset Type Description
0 Byte Boot record Indicator, must be 0
1-5 Byte ISO-9660 Identifier, must be "CD001"
6 Byte Version of this descriptor, must be 1
7-26 Byte Boot system identifier, must be "EL TORITO SPECIFICATION" padded with 0's.
27-46 Byte Unused, must be 0
47-4A Dword Absolute pointer to first sector of Boot catalog.
4A-7FF Byte Unused, must be 0

欢畅

How diskem1x.bin works
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The loader (loader.bin) is the Default Boot Entry in a bootable CD-Rom Boot Catalog. This will load loader.bin into the default load address (0:7c00h). The first thing loader.bin does is move itself out of the way to address 5000:0h.
Loader.bin searches the root of the CD to locate diskem1x.bin. When found diskem1x.bin is loaded into the default load address (0:7c00h). The first thing diskem1x.bin does (also) is move itself out of the way to address 5000:0h.
Diskem1x.bin searches the root of the CD to locate a command file called diskemu.cmd. When found it is run as if it was run using the "batch" command. When diskemu.cmd is not found, or the shift key is pressed while diskem1x.bin was loading, diskem1x.bin presents a command prompt.
You can start floppy emulation or chain-load some other loader or image using the "run" command

紫狐

能翻译成中文的吗？

hola

這個文章應該是 Diskem 1.X 的功能說明吧！我英文菜菜的.......

欢畅

光盘是怎样启动的
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首先要在光盘的 Sector 17 放进一段 CODE。這个区就是 Boot Volume Descripter　 ， 它要指向一个Boot Catalog，也就是 BOOTCAT.BIN 。
在 Sector 17的 OFFSET 第 47h 的位置，要放进 4 bytes 的资料，它就是　 BOOTCAT.BIN 的地址?(Logical Block Address )。
也就是说，由 Sector 17 的 Boot Volume Descripter 指向 BootCatalog 的地址。然后到了 Boot Catalog 后，它又要再指向 Boot Image 的地址，也就是 OSBOOT.IMG 的地址。
等到跑到 osboot.img 后，它就会还原变成原來的软盘內容，然后执行开机。简单说明如下:

Sector 17 ( Boot Volume Descriptor )
---找到--> Bootcat.bin (Booting Catalog)
---找到--> Osboot.img ( bootable image)
-----> 光盘开机
嘿嘿。。。。
简单吧

jinhawk

不错！

甘蔗林

可以实现一张盘多个 IMG 文件即多操作系统吗？
我有这样 的一张盘，只是不会做。
是DOS622和PWIN97的DOS。