Use chkconfig. I'm speed boot times disabling some services. On lastest Irix boots too slow when you are not connected to the internet router, because check internet services and if not found retry some times until continue botting.
First of all I'm suggest activate verbose mode to view what services starting and what Irix doing during boot. In terminal windows type "chkconfig verbose on".
Usually open terminal window and type "chkconfig", it show a list of startup services , some of them are on and other off. For disable some services like timed type "chkconfig timed off".