You'd understand if you were afflicted with the "distnoted" process bug, as many have been with El Cap. On both of our brand new iMacs, this process randomly freaks out and sucks up all of the processor cycles. It happens routinely and can usually only be recovered with a hard restart. I have never seen a more serious bug with any version of OS X, including the very early ones. Some said the problem went away when they installed a Sierra beta so I am hoping it has been tracked down and fixed and rolled into this update.