did you run the magician software on the evo and select optimise os and change the SSD for performance? (or any of the other options)
this changes all the power saving settings so windows might have had the settings changed to not idle the cpu
check the processor power management under the power options
go to control panel, click on power options and then you will see your active option, if its been ran under the magician software you will see one called Samsung.
click on change plan settings on the right and then change advance power settings down the bottom left, you will see a section for the CPU which is called processor power management