Clocks and Timers

Hi, If I have the following XML section does this imply that presence is default of on for rtc and pit? <clock offset='utc'> <timer name='rtc' tickpolicy='catchup'/> <timer name='pit' tickpolicy='delay'/> <timer name='hpet' present='no'/> </clock> Are there any other reference guides to best setup of timers apart from the XML document for different OS types? Regards Simon.