I just started to try to overclock my S9s from different batches.
On one 14TH model from march or so I applied the fixed frequency firmware and ramped the frequency now up to 750 MHz so far. No significant HW errors, hashrate is over 16.2 TH at 85°C chip temperature.
Are the chips really capable to do so much more?
Interesting: Tried a second S9 from the same batch. On the fixed frequency firmware temps go up to 105° C on default 650 MHz. Flashing back the autotune
Edit: 3 of 4 S9 14TH get over 100° after flashing fixed freq. firmware. Any idea why? One even showed 132°. I dont know if that is correct at all.
I did not wait and stopped the miner by deleting the pools and flashed the autotune FW again.
I heard that someone say that downgrading to november firmware can fix some issue like wrong temp reading and other miner firmware issues.
The bad thing on overclocking miner without proper air circulation or cooling device your miner can exceeds higher temp that can lead to higher temp protection and also, chips or the hashing board may burn and damage.
Did you try this method https://bitcointalksearch.org/topic/solution-for-antminer-s9-fans-speed-up-down-every-20-seconds-2690140
you can modify the fan speed of autotune firmware then set it to higher speed it may help to cool down the miner.