retrocomputing

El Torito:

El Torito is an extension designed to allow booting a computer from a CD-ROM. It was announced in November 1994 and first issued in January 1995 as a joint proposal by IBM and BIOS manufacturer Phoenix Technologies. According to legend, the El Torito CD/DVD extension to ISO 9660 got its name because its design originated in an El Torito restaurant in Irvine, California.

A 32-bit PC BIOS will search for boot code on an ISO 9660 CD-ROM. The standard allows for booting in two different modes. Either in hard disk emulation when the boot information can be accessed directly from the CD media, or in floppy emulation mode where the boot information is stored in an image file of a floppy disk, which is loaded from the CD and then behaves as a virtual floppy disk. This is useful for computers that were designed to boot only from a floppy drive. For modern computers the "no emulation" mode is generally the more reliable method.

I vaguely remember fighting with getting burned OS install discs to reliably boot. Another fun thing from around that time is if you happened to plug in the floppy drive cable backwards any disks inserted would be erased. That's a great way to accidentally nuke your boot disk and be screwed if you weren't near another working machine with a floppy drive. Lots of little headaches like that really drilled in the concept of redundancies and lots of backups (as well as not mindlessly installing a floppy drive).