CD-Rom Wiki Pages

[AJ]

Hi All,

Over the past two days, I have fleshed-out the ISO 9660 and El-Torito wiki pages so that they are now "Works in progress" rather than stubs.

There is certainly a lot of information still missing and things could be made a bit "friendlier" not to mention that some proof reading would be appreciated - I have personally written very little iso 9660 code, so a proof read from someone more familiar with the standard would be excellent. If anyone wants to add anything about emulation-mode El-Torito, even better!

I plan to add more detail over the next few days, but there should be enough information there to make a start on a very simple no-emulation boot loader for those of you who already know a bit about basic boot sectors.

Cheers,
Adam

[Edit - typo correction]

[Combuster]

I collected a bit of background info into http://wiki.osdev.org/User:Combuster/CDRom_BS - I never figured out how the CIRC codes work exactly so I didn't round it up and copy it to the main namespace yet.

[AJ]

Ah - thanks for the link. As you can see, I've only dealt with the software stuff because I don't know anything about the hardware stuff. I'll leave that to someone else

Cheers,
Adam

[Brendan]

Hi,

Over the past two days, I have fleshed-out the ISO 9660 and El-Torito wiki pages so that they are now "Works in progress" rather than stubs.

I'm not 100% sure, but as far as I've been able to determine the Boot Information Table (mentioned on the El-Torito wiki page) isn't part of any specification and isn't required by any BIOS. My OS's CD-ROM boot loader doesn't use it (and works on everything I've been able to test it on), and if I remember correctly the CD boot loader used by Windows NT (and later) also doesn't use it either. As far as I know it's a hack that's needed by isolinux (basically it could be considered a useful optional thing, but it's not required for alternative OSs)...


Cheers,

Brendan

[AJ]

Hi,

Thanks - I'll fix that. The main reason I always use the boot information table myself is because the [[Mkisofs]] wiki page uses a command line that automatically adds the table. Correcting now...

Cheers,
Adam

[AJ]

@Brendan: While we're on the subject, I have mentioned in the article that if you are no-emulation El-Torito booting, the int 0x13 extensions will almost certainly be there. Am I correct in thinking that, or should I remove this statement?

Unfortunately, all my test HW is fairly modern, so can't really put this to the test.

Cheers,
Adam

[Brendan]

Hi,

@Brendan: While we're on the subject, I have mentioned in the article that if you are no-emulation El-Torito booting, the int 0x13 extensions will almost certainly be there. Am I correct in thinking that, or should I remove this statement?

I think that's a safe assumption - The Enhanced Disk Drive Specification (Phoenix) was first released in January 1994 while El Torito was first released in January 1995; and El Torito does say:

4.2 INT 13 Function 48

The IBM/Microsoft INT 13 extensions use function 48 for returning drive capability information. The Phoenix Enhanced Disk Drive Specification adds to this information by providing a pointer to a table which contains extended drive information. Byte 10, bit 6 of this table is set to 1 if the attached device is a CD-ROM. This function gives software residing on a CD the ability to determine that it is running from a CD-ROM.

Cheers,

Brendan