grub and real mode int13

[Toerless Eckert]

This is really just a bunch of questions, not a bug report,
but i could not find a mailing liste that would fit better, so
excuse me if i should be abusing this mailing list with this letter:

I was wondering about Grub, INT13 and X86 Real Mode execution:

- I've been trying to set up FreeBSD (without grub) to boot off an IDE
  raid controller (for which there's a nicely working driver in freebsd),
  but i had to give up trying to boot freebsd from it (windows boots fine
  from the controller).  FreeBSD's boot2 stage bootloader hangs immediately
  when executing INT13. Inquiring with the FreeBSD folks the reason seems to
  be that boot2 as well as loader (3rd stage of FreeBSD bootstrap) are
  running in a virtual x86 environment and INT13 is not executed in real
  mode but instead from this virtual x86 environment.

So, now i'm trying to figure out whose fault this is, and wether i
can find an alternative for booting FreeBSD from this Raid controller:

- I could not find any information about how Grub executes INT13,
  eg: wether in real mode or in virtual x86 mode on the official Grub
  web pages, and i have to admit i'm not enough of a x86 assembler expert
  to figure this out from assembler source.

  => How does Grub execute INT13 interrupts ? Real mode ? 

- The following url
  http://www.pvv.ntnu.no/~steinarh/grub/prog-ref.html
  seems to indicate that grub not only uses Real Mode, but also that
  INT13 is always only to be executed from Real Mode. That was my understanding
  too, eg: Is there any specification from let's say Microsoft/Intel/IBM
  or so that details as to wether INT13 is supposed to be supported from
  virtual mode ? Or rather the opposite ? I'm just wondering how bold
  the FreeBSD bootloader are in trying to do this...

- Last but not least: Even if Grub is able to correctly boot via INT13
  real mode, then i would still not be able to use it today because it
  can not directly boot the newer FreeBSD kernels but can only boot the
  3rd stage loader from FreeBSD, which itself will of course again have
  the Real Mode INT13 problem ?

Thanks 
    Toerless Eckert