another question: what can break?

[Mark Meade]

Erich Schubert wrote:
> as far as i now understood the way the old firmware probably chose was
> to hook the disc handler 13h which would mean that it has to emulate a
> real block device, is that correct?

Yes.

> Where do i find the old firmware, in case i want to restore the original
> contents of the flash?
> is that in DOC52.EXB in the ttfs_5.1.2 package from m-systems?

Yes, you can use the DFORMAT command in the M-Sys DOS utilities to restore 
the original contents.  Using the newest versions of DFORMAT (5.x) prior to 
installing Grub may cause problems (UnitSizeFactor != 1) -- but the earlier 
versions (4.x) should work fine for now.