maacruz, Thanks !

Exactly what I wanted to know.

Yes, a search for 0xFFFF certainly pointed to several uses for it.
A couple of hours of reading, and I began to understand the possibilities.

Also,
I found a reference to an ARM version of 0xFFFF by qwerty12,
and a reference in linux.softpedia.com (2008) that 0xFFFF had stable support for N800,
but not yet for N810 and a warning that Nokia might make changes.
And no release since 2007 in garage.maemo.org ...

I get the impression that on an N810 I should use 0xFFFF only for experimenting,
and if that is the case I think I'll leave it for now.

There is no ARM version of the standard Linux flasher, is there?
I happen to have two N810:s but at the moment no other running computer.

So I guess I had better ask a neighbour to let me use his PC for a normal reflash.

A question,
if I learn some more Linux and decide to go wild and try something with 0xFFFF,
is there a risk of damaging the N810 beyond the possibility of a standard reflash?


( The momentary reason for all this:
I had a backup of original OS 43-7 (made with Console Tools), but while restoring it I accidentally restored to the usb stick and wiped it. And I had no copy.
As in the classical cartoon: [delete?], OK, [are you sure?], OK, [file deleted], NOOO, what did I do...
When will you ever learn.)

About learning Linux in general ...
Yes I agree, a "normal" Linux with good support for beginners makes a good start,
but a barebone Linux would be easier to try to penetrate.
Experimenting with the tablet - my first contact with Linux - has certainly taught me a lot.
The forum howtos on e.g. advanced booting and cloning will probably make good future lessons.
( Now I use Penguinbate's very functional Console Tools and Qole's Easy-xxx.)

But good reading on the Linux file system is hard to find.
Any suggestions?
(My previous experience is digging into and tinkering with RISC OS (on the Acorn Archimedes), which was very logically structured and much simpler.)

Thanks again,
KristianW