Miguel Masmano UPVLC mimastel@doctor.upv.es Ismael Ripoll UPVLC iripoll@disca.upv.es 2005 OCERA Consortium Please, visit the site www.xtratum.org for up to date releases. OCERA Xtratum Nanokernel, multiple-domain multiplexed XtratuM is an open source nanokernel (or better a picokernel) that goes beyond the classical ideas of nanokernels (www.xtratum.org). Basically, XtratuM is just two simple device drivers: interrupt and timer. It can be used to replace the current HAL of RTLinux, avoiding the RTLinux patents, as far as we reckon.