2 miners turned down to 50% of its default power consumption do better than 1?

[Dr.Detroit]

I have a handful of S9 miners and have installed Braiins" on them an have been playing with some settings and I have found that running them at 50-60% and playing with the HZ of the hash boards and voltage.. that I seem to be doing better than running one "overclocked" im sure there are plenty of things involved with the HZ and voltage settings I don't know does anyone have anything to add to this? and "yea having 2 miners to just get ones output is "BACWARDS" but for a non profitable cheap miner anything helps. thanks all!

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[sidehack]

Power use for increased hashrate isn't linear. The marginal increase in power use grows as hashrate increases. To run a higher clock speed, you need a higher voltage to have more juice to make all the transistors switch faster, but a higher voltage also results in a higher current draw, which means that since power is current times voltage, and both are increasing, you get an exponential increase. Like if it runs 1V/1A at 1GH the power is 1x1=1W, but if to get 1.1GH you increase to 1.1V, the current increases to 1.1A so power is 1.1x1.1=1.21W so you see an 21% increase in power use for a 10% increase in work.

Same the other way. If you decrease the voltage from 1 to 0.9, the current drops from 1 to 0.9, and now power use is 0.9x0.9=0.81W so you see a 19% drop in power use for only a 10% drop in hashrate.

That's not real numbers, by the way. The actual interactions are a lot more complex, but it's a conceptual illustration. When you undervolt and underclock something, the power use per hash will decrease more than the linear decrease in hashrate. So yes, two undervolted S9 at half power should have a higher hashrate than one S9 at full power, because the chips are running more efficiently.

There's also additional benefits from running colder reducing the current load, but that's a less obvious effect.

[Dr.Detroit]

thank you for the reply! that was more than I was expecting I am grateful!
im putting use to some old S9s and just playing around. it dries clothes great.. lol door closed it vents outside, door open its a great heater, door closed and "running it dries close "almost just as fast" ITS CLOSE. it pulls the heat from the miner with its "normal" exhaust and I the miner has enough pressure to just vent outside when the door is closed and the miner is on "like after the cycle ends..

[hZti]

I run my S9 at 650 Watts and get an efficiency with brains Os+ of around 77 Watts/Ths. So if you have many of them that you can’t use no more this is a great option. Also 650 Watts allows a very silent fan.
By the way, after going below around 700 Watts the efficiency actually goes down and is at 550 Watts already at only 80+Watts/Ths.

[sidehack]

At that point, the fixed load of fans and controller probably start to become a more significant part of the overall power draw. It's kinda like how at low speeds in a car, rolling resistance will dictate your energy use more than wind resistance though wind resistance dominates at high speed.

[hZti]

At that point, the fixed load of fans and controller probably start to become a more significant part of the overall power draw.

That is true, with an antminer S9 you have a minimum power draw of around 70 Watts for the controller and PSU no matter the hashrate.

[DaveF]

At that point, the fixed load of fans and controller probably start to become a more significant part of the overall power draw.

That is true, with an antminer S9 you have a minimum power draw of around 70 Watts for the controller and PSU no matter the hashrate.

Also don't forget the efficiency of the power supply vs rated output.

Getting the cheapest thing you can find out there vs an 80 plus Titanium may be better then dropping from 750 watt to 650 watt.

There is obviously a large cost differential between the cheap and best power supply, but some of the cheap ones are so bad that no matter how well you tweak your miner someone running one stock but with a top of the line power supply will beat you in efficiency.

-Dave

[philipma1957]

you can cheat a bit with 1 fan using braiins.

and some fans will cool it enough and pull less watts.

https://www.amazon.com/SilverStone-Technology-Computer-Cooling-FHP-141-x/dp/B098KRT5ZM/ref=sr_1_2?


the fan above can cool up to 650 watts and burns less power

just set the braiins to 1 fan

there is a decent delta that works well somewhere some place I have a thread and links for the delta.


sometimes best buy sells good quiet 850 watt seasonic psus that are good for these units.

[DaveF]

At that point, the fixed load of fans and controller probably start to become a more significant part of the overall power draw.

That is true, with an antminer S9 you have a minimum power draw of around 70 Watts for the controller and PSU no matter the hashrate.

Also don't forget the efficiency of the power supply vs rated output.

Getting the cheapest thing you can find out there vs an 80 plus Titanium may be better then dropping from 750 watt to 650 watt.

There is obviously a large cost differential between the cheap and best power supply, but some of the cheap ones are so bad that no matter how well you tweak your miner someone running one stock but with a top of the line power supply will beat you in efficiency.

-Dave

Just did a bit of a test on a GPU rig.

Using a totally crap no name 1000W power supply running benchmarks was pulling 810W at the wall average with a max pull of 838W
Using a EVGA SuperNOVA 1000 T2, 80+ TITANIUM 1000W running the same benchmark 779W at the wall average with a max pull of 800W

Make of those numbers what you will.

-Dave