Have my two S5 up and running with overclocking stable so far. Both are connected to a CX750M PSU each.
Optimal overclocking settings (Frequency) has to be determined for each unit seperatly with try and error.
I have now one running at Freq 400 resulting in 1.3TH, the other one runs at Freq 393.75 resulting in 1.26TH.
What I figured out is, that you should look out for the HW error rate. As long as it's in the 0.0xxx% range, it's ok. As soon as the HW error rate reaches 0.xxx or higher, the Hash rate drops.
So in my case, when I set the Freq to 400 on my second S5, the Hash rate drops from 1.26 to 1.23 while the HW error rate climbs from e.g. 0.0376 to 0.2135.
And it gets worse the higher I set the Freq.
Of course you have to watch temperatures, which is in my case not a problem, running cool at 45/48 with Fan at 3240 rpm in ambient temp of 16C (loud yes, but in the basement so I don't care).
So my advice for overclocking: I would start with a Freq of 375, let it run for about an hour and monitor temp, hash rate and HW errors. If all is fine, go one step higher etc. until you see a drop in the hash rate along with the above explained HW error rate (or your temp goes through the roof).
Hope this helps.
6.25 less in frequency makes you win 30 GHS
