ok, sorry for misunderstanding. 
RTIME quantum=3; 
is working.
quantum  The round-robin quantum for the task expressed in ticks (see note). 
Howewer, there is no link to the mentioned note. It will help to understand the tick concept. 
 
Best regards,
Olivier

Le 09/11/2011 12:02, Gilles Chanteperdrix a écrit : 
RTIME quantum=rt_timer_ns2tsc(3*SPINTIME);