Oh let's see. I think there were three firmware versions.

The first Monarchs only seemed to work with BFGMiner 4.20 on Windows. It was weird, there were sync issues with all the little engines talking at once that blew up other versions with queue mismatch errors between requested work and produced work. I spent some time whacking away on the BFG code and I think I got it to work with later versions but it really wasn't worth the effort. Setting a very high difficulty helped here as the engines would not all be replying at the same time when they had a lot of work to do. But this caused stale blocks with P2Pool. Which doesn't exist anymore......

Second version was the best, worked with CGMiner and most others. I dont recall a third firmware version.

Changing firmware was not very easy, they made hardware changes through the runs and reflashing a Monarch board with different firmware would result in a bricked miner. Double fun was that the boards weren't easy to tell the difference from (other than when they went to the high frequency metal FETs on the later boards.)

I'd say just fire it up and let the pumps circulate to keep the rubber gaskets in those water blocks pliable. I still have the 4.20 code for the first generation miners if anyone needs it.