On Tue, 2 Dec 2003, Chris Adams wrote:
Once upon a time, James Olin Oden joden@malachi.lee.k12.nc.us said:
Actually, I believe ISOLINUX is still doing the "El Torrito" Bootable floppy image thing, but the image contians a "syslinux" boot loader smart enough to read from the cdrom drive to get its configuration.
SYSLINUX doesn't know how to read from CDs. ISOLINUX is different; it does not use a bootable floppy image, however it still uses the El Torito extensions (it doesn't know how to read from the CD itself).
El Torito specifies several BIOS extensions for booting from CD; the most commonly used (and most commonly supported) is to put the image of a bootable floppy and have the El Torito extension read it and emulate a floppy drive. Some computers that support El Torito extensions only support booting from a floppy image.
ISOLINUX uses a "no emulation" mode, where BIOS INT13 calls can be used to read blocks from a CD (more or less like reading from a hard drive in real mode). ISOLINUX does know how to read a basic ISO9660 filesystem to find the files.
Not all computers that support booting from a floppy image will boot from a "no emulation" CD, but most do. IIRC, for RHL9, the second CD was also bootable, using a floppy image for the computers that didn't support the other way.
Thanks for that explanation. Some things that were mysteries to me are now explaned.
Cheers...james