So if I understand it correctly, best efficiency(W/TH) is mainly based on voltage, right? Therefore I should try to run them all on 7.9 and tune the frequency?

I'm sorry to hijack this tread, but can someone share lowest possible settings for S9 with Brains? One of my miner is able to run 500MHz@7.9 (10.5TH) with 880W consumption at ~240V. Others do 500MHz@8-8.2V with 930W+.  I guess you can go lower with frequency, but as far as I know 7.9 is lowest possible voltage for S9.

The issue was indeed broken fan. I can confirm, that temperatures in latest BOS are reported correctly and miners are restarting once temp2 hits 95C. Thank you for your help with downgrade command, maybe someone else will find it useful.

How do I downgrade to BOS 2018-11-27 from 2019-01-24 on S9? I found


but 2018-11-27 is no longer available on https://feeds.braiins-os.org/

With latest firmware one of my miners is restarting due to high temperature (was working correctly before update).

I don't think is a good idea to power off and cool it down quickly with fan running. It is a big thermal shock for PCB, chips etc. You better let it cool down slowly.

- yes
- yes, put it exactly as I wrote it (including stars)
- "0 */6" stands for "every 6hours at 0 minute" (0:00, 6:00, 12:00, ...). If you want to test it for example at 10:05PM you should  put "5 22 * * *" (it uses 24h format, 10PM=22hours).

I tested it via SSH and command you want to run is /etc/init.d/cgminer reload as root. I believe that you need to add


to BOS Scheduled tasks and restart miner to load crontab changes. That command will reload cgminer every 6 hours (please refer to https://crontab-generator.org/ to understand crontab syntax).

EDIT: I just tested it and its working like a charm.

Hi taserz, any chance you find a time to compilte that 870mV binary? I would love to try that on my S9i.

PS: I will defo send you some donation soon. Very good mod. Thanks!

You run 800MHz @9V right? I guess my meter would measure like 1900W. I might try that once ambient temps are lower.

I have another question. One of my S9 (01/2018 batch) is having trouble to keep up hashing on 2 boards above 700MHz. It is hashing, but RT is much lower than ideal. Is there some tool for S9 like for A3/D3 (https://bitcointalk.org/index.php?topic=4032178.0) which can increase PIC voltage on specific board? Thank you.

Hi, thank you very much for that firmware. I did some testing with 880mV version and measured the energy consuption at the wall using energy meter. Not sure if it is super accurate, but its just for comparsion. I'm running all miners in oil, but PSU (original bitmain 1600W) are outsite and ambient temp is quite high (35C/95F during day now), therefore I'm not going to run those PSUs at 120%.

S9i (running its original autotune FW)
stock 14TH@1450W
- 675MHz 14.5TH@1530W
- 725MHz 15.6TH@1650W
- 750HHz 16.1TH@1710W - I will be running this setting, HW errors in single digits per hour
- 775MHz 16.7TH@1770W

S9 (original autotune FW, 03/2018 batch I think)
stock 13,8TH@1480W (900mV,900mV,910mV)
- 700MHz 15TH@1580W
- 725MHz 15.6TH@1650W
- 750MHz 16.1TH@1700W



Interesting thing for me is, that temperature on those S9i increased only about 1-degrees, but on S9 it is now +20C (61->81). Do you have any idea why? Does it have something to do with "TempTypeID=1a middle offset=-51"? Maybe those older boards should have different offset?

Also, will you be so kind and compile 870mV FW and put it on github? I would love to try lower voltage and higher clock speed, as I'm oil-cooling it I have no problems with overheating.

You will be fine with 7Mbit..

Here you can check some stats of full node running https://statoshi.info/
Specifically bandwidth is this graph https://statoshi.info/dashboard/db/bandwidth-usage

just simply fake the fan speeds and you are done.. you can use this diagram https://www.techidiots.net/notes/fake-fan-sensor  1uF and 4,7kOhm will tell antminer that fan is spinning at 4400rpm.. I use this on S9, L3+ and A3 in my custom oil cooling setup..