Man I hate these 2 S3's I have that wont mine at 500gh/s.
I put them at 250 and they mine at 470ish, put them at 243 and they mine at 492.

But after a few weeks I stare at them and think, why dont I try 250 again! so I try it and bam 470ish, then I put them back to 243 and they sit at 480 until I start stop cgminer a few times then they go back to 492.
  Maybe I should try restarting cgminer with them at 250... in a few weeks...