I am running a few old miners (T9+) to heat my home and they are too loud and making a loss (which is ok, as I am interested in the heat). Following this suggestions (sticking with the standard firmware) I already reduced the fan-speed by adding the following entries to /conf/bmminer.conf

"bitmain-fan-ctrl": true,
"bitmain-fan-pwm": "66",

This resulted in an increased temperature of the chips (still below 100 deg C) as can be seen here: enter image description here

coming from here (below 80 deg C):

enter image description here

Since I am still not too happy with the noise level (reduction from 75db to 60db) thus I am considering to under clock the miners.

I believe that the frequency and Hashrate should follow a linear / proportional law meaning that reducing the frequency by 20% from 550 to 440 should result in a reduced hash rate by 20% from 10.5 to 8.4 TH/sec. Can someone please confirm this?

I am actually more interested in what is the relationship to power consumption. I am currently mining at a loss meaning I can't afford the same energy cost at a lower hash rate. I read that overclocking is not economic as the energy consumption does not grow linear.

  • Would that even hold true in the other direction?
  • Could the mining cost even break even (neglicting hardware cost) if I would reduce the frequency by 50 or more percent?
  • Where can I find a plot to measure this effect or how could I create one? (I am not a electrician)

The degree of efficiency (J/TH) is directly related to the microchip design and does not follow a linear path. The T9+ uses a 16nm, whereas the newest Antminers are thought to use a 7nm. Their efficiencies are 136 J/TH and 30 J/TH respectively. The curve is exponential decay. Older machines become redundant due to difficulty increases.

The high decibels are due to the fans, and these are very important as too high temps damage the microchips, ultimately leading to a hashboard failure. The best way to tackle noise is by under clocking, using immersion cooling, changing the fan, or designing a silencer box. But these methods only get you so far as you discovered.

And, if you heat your house then you can compare the electricity cost to the cost of heating, as Satoshi did in 2009: "The heat from your computer is not wasted if you need to heat your home. If you're using electric heat where you live, then your computer's heat isn't a waste. It's equal cost if you generate the heat with your computer. If you have other cheaper heating than electric, then the waste is only the difference in cost. If it's summer and you're using A/C, then it's twice. Bitcoin generation should end up where it's cheapest. Maybe that will be in cold climates where there's electric heat, where it would be essentially free."

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