p4 pulls completely off 12v rail. hence the 4 pin yellow and black plug for the processor. i am using a p4 1.7 mobile chip which runs less heat and less power its only 33 watts or some **** so i figure 3amps on the 12v rail. calculate how many watts the processor is and how much it will pull from the opus' 12v rail. remember opus can only handle 5a on the 12v. im running a 8 inch lilli 7200rpm 200 gig drive and the cpu off 12v and it all works fine.