Why would you use 9V psu? 12V psu is more commonly available than 9V psu.
he wants to under volt and under clock the s-3 to get better then .8 watts per gh at the kwatt meter.
this can be done to the s-5 with a 9 volt psu .3 watts per gh at the kwatt meter is supposed to be possible instead of getting .52 watts at the kwatt meter using a 12 volt psu.
No one has shown it to work on the s-5 as of today (I could be wrong)
Also this won't work on an s-3 it need a mod like that of the s-1. but you need to really do a lot of labor to do it. plus the s-3 improves from
0.8 to 0.6 with a much more labor intensive mod then the s-1
the s-1 went from 2.0 to 1.1 with an easy pencil mod. a solid improvement with very little work.