# BIOS storage access through INT13H

The units at [drv/pc/int13hl.fs] and [drv/pc/int13hc.fs] implement a driver to
access the boot drive through the BIOS INT13H call. One is for LBA mode
(required for a partition deployment of Dusk) and the other is for CHS mode.

They implement "biossec@ ( sec buf -- )" and "biossec! ( sec buf -- )" as well
as the "bootsec@" wrapper for "biossec@" (for [io/secld]).

These words can be used to create a [io/blk] structure that can then be the
mounting point for a filesystem [fs/core]. Example:

  :> drop biossec@ ;
  :> drop biossec! ;
  BOOTSECSZ -1 newblk newfatfs bootfs!

This driver is probably unreliable (it has to go in real mode and the process
for doing so is very very hairy. I'm not sure of how solid it is.) but will work
on all PCs until a better driver is activated.

## Overriding this drive

As we write above, this drive is unreliable and you'll want to use a proper one
as soon as possible, likely in your init.fs file. Because the underlying drive
is the same with the same contents, no need to remount a filesystem, just to
swap the underlying storage (see [fs/fat] for fatstorage!):

  mynewblk bootfs fatstorage!
