Quote from: akadamson on February 19, 2018, 10:21:12 PM

Quote from: tf315 on February 19, 2018, 10:02:27 PM

Quote from: akadamson on February 19, 2018, 08:45:37 PM

Quote from: HagssFIN on February 19, 2018, 08:43:58 PM

Quote from: akadamson on February 19, 2018, 08:37:25 PM

Sheesh, fans set for 100% all the time in the 821 firmware... Anyone played with setting it back to something reasonable like 50% or 20, like I ran the 741's and let the temp circuit moderate the fan speed as needed to keep 90 degrees on the outlet? I guess I'll see what outlet temps I've got first, but my basement this time of year is pretty dang cold, and I'd just as soon trade off some noise if appropriate.

What's your 'minimum fan speed' setting in the Cgminer configuration?
I'm guessing it is 100.
Set it to 20 and see how the miner acts in your environment.
Note that 20 is only the minimum value and miner will control the fan speed up or down in relation with the miner temperature.

yes, by default the firmware has 100% in that min fan speed and I suspect I know why, the internal temp that they attempt to keep the outlet at is 70 and to do so, it appears to take 100% fan typically.

You can put something like:

--avalon8-fan 1-80 --avalon8-temp 90

in the 'More Options' box if you want to change the target temperature and fan speeds. Haven't played around with it too much but 80% fan speed still kept mine at a reasonable temperature so far. The difference between 80% and 100% fan was only a couple degrees after a few minutes.

Yeah, but I wonder if they are *trying to keep* the outlet temp at 70. The 741 runs at approx 90 and thats what set value it has in the cgminer code. So someone must want the 821's to be at 70. I'd hate to adjust that and burn up an 821. I suspect the current/voltage changes pretty dramatically as the temps rise on the ASICs. And from others testing, the -1 undervolt has the opposite effect - hashrate and wattage goes UP, not the other way around... Be curious of others findings?

Bit more info here after running these for a few days.
a) I would change the "min fan speed" in the configuration to 50, from the 100 as the firmware came
b) I would *NOT* change the max temp from the default of 70.

I went back through all the git merges on the 821 code and that max temp was specifically changed from 90 which the 741's ran at to 70 and my guess is they want to keep the chips *COOL* and not let them get hot. The 105 number is still in there as the autoshutdown number, but that's a pretty scary temp and I would avoid at all costs letting it get much above 80 or 90 for any length of time.

Because they are trying to keep the ASICS cool, if you shut one down that 50% min fan will still force enough air over them to cool them. The problem with aluminum is it works both ways, it will dissipate heat when used to cool, but if not cooling it will hold the heat and cook things.

By lowering the min fan to 50, if your environment will allow for an inlet temp that can keep the outlet at 70, with a lower than 100% fan, the fan moderation will kick in and you'll save some noise.

I noticed this today, my room temp was way below 30, and the outlet was 70, but the fan was at 85% which was way better than the default of 100 all the time.

Just remember, you don't want them above 70 for any length of time (or so it would appear that Canaan doesn't) but if your environment will allow you can drop down the min fan. But leave it at something that would rapid cool the headsinks if the unit drops offline or is stopped.

ps. this is why I pretty much go to an *unplug enet* when I want them to shut down gracefully. This keeps the rPi controller in the loop and once they run out of hash, they go to the min fan temp while they cool. Then I can unplug the I2C cable and turn them off.