Efficiency doesn't change much with clock speed because although dropping the clock reduces power consumption, it also reduces hashrate, and both are approximately linear effects. The way to boost power efficiency is if you could also undervolt- something that apparently does not work well at all on the S5.
The BM1384 chip on the S5 theoretically allows significant undervolt but even apart from the difficulty of finding high efficiency 8-10V power (required as the S5 is a string miner) the S5 has something which evidently just doesn't work if you drop the voltage much. Sidehack has said he suspects the (chained) clock line, at any rate some of the chained signals and the related I/O voltages are most likely suspect. As far as I know no one has taken the time to mod an S5 to be able to undervolt or could tell you what is going wrong for certain.
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novak
The BM1384 chip on the S5 theoretically allows significant undervolt but even apart from the difficulty of finding high efficiency 8-10V power (required as the S5 is a string miner) the S5 has something which evidently just doesn't work if you drop the voltage much. Sidehack has said he suspects the (chained) clock line, at any rate some of the chained signals and the related I/O voltages are most likely suspect. As far as I know no one has taken the time to mod an S5 to be able to undervolt or could tell you what is going wrong for certain.
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novak
My results are 0.44w/GH par 11.1v
Under 11v. Miner starts but dies after a few minutes.
At 10v and lower, it doesn't start hashing., but you have access to the web interface.
Stock efficiency with the same PSU is 0.54w/GH
I suspect the s-6 will allow good numbers which is why they did not alter the s-5 to allow for a 10 volt psu to attach to the s-5 and work.
