A921 and A851 best underclock configs to decrease temp

[s_falahati]

Hey,

It's hot here so I decided to undervolt and underclock my miners to try to keep them a little more cold in the summer but I am afraid I can't do that very well. By searching the forums I figured that apparently I have the worst possible models to underclock in all the history of miners so here I am asking if anybody had some success with underclocking these miners.

Please keep in mind that the only important thing here is the temperature of the miner and therefore the power burned by the miner and not necessarily the efficiency of it. For example, A921 is normally like 100w/Th and takes 2Kw from plug to generate 20Th; but I don't care if it generates 15TH at 120w/Th as long as it decreases the overall power usage and therefore the temperature while decreasing the hash rate to a reasonable extent.

My A921s are currently on the latest MM and controller FW and using the following config:

Code:

--avalon9-voltage-level -2 --avalon9-voltage-level-offset -2

I get around 18Th for 1.9kw

I failed to underclock my 851s which are on the latest MM and controller FW properly. I can get down to 1.5Kw but the hash rate drops to like 6Gh which is insane. Didn't tried the `Balanced` or the `PowerSaving` modes introduced in the latest firmware yet.
It seems that whatever `--avalon8-voltage-level` I try (even 0) produces the same result.

[PassThePopcorn]

I'm going to assume you mean TH instead of GH.

The latest pi firmware and MM for the 851 will lower the power usage, the 3 modes that they provide are just default frequency and voltage settings which can be over ridden by the user.
Can you post the cgminer log file? (copy paste it inside the code tags you can use them in your post by hitting the button that looks like # in the formatting options)
Have you also tried changing the frequency while changing the voltage?

[philipma1957]

the A841  was great

the a851
the a921 not great

My a921 is in a remote area and power cost is low enough I gave up trying to get  good number on it.

I let it run.

[NotFuzzyWarm]

@ OP
You might want to take a look at the tests I did a few months ago on the A921 here