[syslinux] Isohybrid wiki page and UEFI

Thomas Schmitt scdbackup at gmx.net
Fri Oct 23 13:41:53 PDT 2015


i see i forgot to answer Ady's question

> is it relevant for BIOS (non-EFI) too?

In theory yes, in practice no.
The Sector Count of BIOS boot images is controlled by
mkisofs option -boot-load-size, which for ISOLINUX is
prescribed to be 4, regardless of the size of isolinux.bin.
I.e. the BIOS loads the first 2048 bytes into memory
and begins to execute them as x86 program.

EL Torito 1.0, 4.3 "INT 13 and Booting" says:
 "The specified number of sectors are loaded at the specified
  segment (usually 7C0), and then the BIOS jumps to the load
  address. The software can retrieve a pointer to its boot
  information by issuing INT 13, Function 4B, AL=1."

I assume that the first 2048 bytes contain enough brain to
load the rest of isolinux.bin as appropriate.

Have a nice day :)


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