[syslinux] memdisk: DOS as a PreOS

[H. Peter Anvin]

Matthew Moffitt wrote:
> This is something I would be interested to see as well.  The 
> 3com/Lanworks environment we used to use had a pboot.exe utility that 
> would unload the DOS floppy environment and roll over the boot to the 
> local disk.  It was handy for us.
> 
> Since switching I get most of what I need by having several memdisk 
> images available and, during the times when we need to boot the 
> floppies, I switch the server side configuration file to reference the 
> different disks for the default boot.  However we then lose our ability 
> to step into the boot process during normal boots since we need to let 
> it come straight from the local disk.
> 
> Anyway, things work well enough but if we could get more control by 
> applying our customizations during a pre-boot environment and then 
> unload it, rolling over to the PC hard drive, it would be ideal.  Would 
> there by any more flexibility working from another OS in the floppy 
> image than DOS?  Something that would allow it to unload when finished?
> 

DOS is tricky since it installs its own INT 13h and INT 15h hooks, which 
means MEMDISK won't be able to unload its stub (typ. 2K of DOS memory). 
  It could, however, unload its storage area and passivize its stub 
easily enough.

	-hpa