Got the same problem as adamg83...
I
rigged up my first 3 s3's last night and they were running at about 450gh/s, so all OK.
Overnight they all went down to about 200gh/s, so I turned them all off and started them again - they then went up to 450gh/s again.
They have been working for about 4 hours and now one of them has reduced again, but at the moment the other 2 seem to be OK.
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Got my S3 two days ago....Working fine for first 24 hrs, then went to < 50 ghs....Rebooted the S3 and it worked fine again for 12 hours, before heading south again to under
50 ghs....Rebooted...Worked for less than 4 hours before going to < 50 ghs....

Didnt reboot this time -
After reading posts, i unplugged my brand new RM650 Corsair, checked the connections, re-plugged it and its working fine again...Note: i don't have a hybrid/normal button like with the AX version...I have two 8 pin to 6+2 pin wires going from the PSU to the S3....
Is there an issue with the Corsair PSU or is it some setting on the S3 that's causing the issue?
My firmware is from "Wed Nov 26 18:04:24 CST 2014 "....
Thanks in advance!