That is because the 755 W is the total your rig is consuming not only the cards. And just for you to know, Linux uses 5% more energy than the Windows OS in mining, yes it is a thing where Linux is behind.
That is the reason why your power meter reads 755 W and I think this is a much normal power consumption in a rig with 4 Gtx 1070 cards.
First of all the Nvidia-emi is not completely accurate, it is an estimate. 755 W is the total consumptions not just the cards. And you have to take into account Linux uses 5% more energy when mining in comparison to windows os. with all that being said it is pretty normal all things considered.
I don't know where you are getting this information from, but we have received multiple reports that ZhashOS which is a pendrive based Micro Linux where it's total size is less than 1 GB and loads completely into ram on boot is using 70-110 watts LESS than windows.
It is probably because CPU utilization is under 3-4% most of the time with this OS and it needs ZERO virtual memory so it is not hammering on a hard drive swap file. Actually, it doesn't even need a hard drive at all which saves a few bucks on the "Total Cost of Ownership" of your rigs.
Here is a tweet from firstminingrig showing power meter results:
https://twitter.com/firstminingrig/status/1010449787802484736?s=19So please don't consider all Linux's to be power inefficient. It can be VERY efficient when it is built to be. Which is what we focused on with ZhashOS. It is also why Linux is very popular in the commercial / Industrial embedded control market. And why Android and iPhone are foundational derivatives of it.
We are getting ready to provide release 3 (release candidate is out now) which will be a HUGE improvement in setup time and ease. We have received a #zhashos discord post that one first time user was mining in around 2 minutes after initial boot.
Here is the Bitcoin Talk discussion forum for other details and a screen shot of it in operation:
https://bitcointalk.org/index.php?topic=4481713.msg40261859#msg40261859ZhashOS is currently providing the asic resistant equihash miners such as EWBF, miniZ,gminer and bminer. Though bminer can also mine ethash.
I hope this clarifies the Linux power efficiency concerns.