I'm sorry if this was already covered...so Ill keep it brief.  I have an AntMiner S3 that's a rockstar.  I overclocked it to 250 MHz, and it was hashing right along at 505-506 GH/s, even after 2-3 hours.  Temps were great 39C-41C, absolutely no X's on my chips.  This morning, I wake up...take a quick peek before heading off to work and it was sitting at 490GH/s, and it was still sitting at 490GH/s (rock steady) when I got home from work 10 hours later.  After work I calculated the HW errors and i'm sitting at 0.21%(pretty good unless I missed the boat).  Now I know that's nothing to complain about...and I'm not trying to.  I'm just wondering if anyone else has experienced a similar situation and has any kind of explanation or trick to get it back above 500.  Thanks.