two on one controller may no longer work as you guessed it the newer firmware breaks that.
It makes for a comedy except you the op are not laughing
Antminer firmware upgrades are really bad very few did anything worth while.
Can confirm that, plugged 6 boards in and only 3 show. DAG NAMMIT!
Can also confirm that I am not laughing
I can't tell the difference on the antminer that is still working, totally not worth it. Unfort I couldn't find anything on google before I did the firmware update regarding this being a bad idea, might just slap some search terms at the end of this message:
Antminer S7 Firmware Upgrade
Antminer S7 Failed Firmware Upgrade
Antiminer S7 Bricked
merry xmas