The only reason would be the manual one at 600.00M freq hashes @ 8.5-8.7 Th @845W
The auto freq one is dead set at 7.5 Th... much quieter and draws only ~800W but would like to have the flexibility of tinkering with it.
I figured Bitmain might have some sort of a check on FW date and wanted to ask before I actually gave it a try.
So I take it there's no known workaround?
I have the autofreq one (Nov 2018) and the boards are set at 600m (or close, one is like 602 and the other 598 or so). In my case, the older firmware would actually do 8 THs vs now 8.5THs.
If you "upgrade" to the old one it should work, but you should not do this. Asicboost makes them work much better. I do remember some R4 batches labeled as 7.5T instead of 8T, perhaps you have one of those?
Flexibility will come, next year after Braiins OS finishes the cgminer replacement bOSminer and they start adding more hardware support. In the meantime, i don't think any other firmware is worth it, you could use the older if the asicboost one is giving you trouble, but i don't recommend it.
This fan is too silent to bother forcing it, and you can always force it to 100% by disconnecting the fourth (blue) wire...