Need Help W/ Energy Setting "Put Hardware to Sleep When Possible"?

i dont understand the "put hardware to sleep when possible" option in the energy saving settings.

isnt that the whole point of the 'computer sleep' slider ? it lets you choose if you want to put the computer to sleep at 1 minute of inactivity, 15 minutes,1 hr, etc. etc.


1.)
why do they also need a "put hardware to sleep when possible "checkbox. is there another function that isnt explicitly stated?

what would happen if i left it checked vs unchecked with the computer sleep setting at 15 minutes?


2.)
on another note, if i want my computer to run all night should i set the computer sleep setting at "never"? or is there a more efficient method.

 

yes sorry i meant hard disk.

if i put the computer sleep option to "never" will unticking/ticking the box that says "put hard disk to sleep when possible" have any kind of effect?

i thought the computer IS the hard disk?

can my hard disk be sleeping if my computer is on "never"?