In ROM3.1 the delay waiting for an IDE disk have been extended. That is why it takes a lot longer before the purple screen gets on. If you had a harddrive installed in the systeme it wouldn't take that long even if the harddrive wasn't formatted or anything. There is a small peice of hardware you can make to get around this problem and fool the system into thinking there is something on the IDE header:
IDE_Killer.lha