Negative HP and Deathless frenzy

[TabulaRasa]

If a 4th level frenzied berserker is reduced to negative hit points during his frenzy he is not killed. He will fight on until his frenzy ends no mater if his hp is negative, because of the "Deathless frenzy" class ability.
But how low will his HP go?
I think that you can never have less then -10 hp but I'm not sure.

Is there an official rule about that?

/Tabula

 

[daTim]

http://enworld.cyberstreet.com/showthread.php?s=&threadid=46342

This was about 5 threads below this one. Hope that helps some.