OSX ML activity monitor. I don't quite understand it: There are two parts the CPU % usage per process in the big table and the 3 figures at the bottom, user, system and idle. Question 1) The figures at the bottom. If the CPU is 80% idle on a quad core machine, this usually means the fans are blasting at full speed ( and volume). Does 0% idle mean 4 cores at 100% and therefore that 75% idle means an effective load of 1 core at 100%? Question 2) i thought maybe main table displaying CPU % per process shows the % of the current CPU load being used by a single process? I.e if the CPU is 80% idle and a process is 100% that would mean it is using 20% of total CPU load. But that can't be right as the percentages often add up to more than 100%. How does the CPU % per process work? Question 3) How come even multicore video encoding doesn't get the CPU past 50% idle yet spins up the fans and temps to the max?