So I did what any crazy person would do and bought me another Monarch on wednesday. This time it was a regular auction on ebay. 230 pounds / 290 euros, so a tad cheaper than my first "550GH" unit.
The board seems to be a different revision. It's a "700 GH" model with a mini-usb connector (which the 550 GH model didn't have) next to the pci-e power connectors.
http://i.imgur.com/Itspqdq.jpgThe problem is that it's running too hot, above 80 C and the board starts throttling after only a few minutes of running. Power draw is 570 watts from the wall at 800 GH/s.
So it would be great to have a method to underclock this thing as I don't really need the extra GH/s with a bigger power draw and overheating.
By the way, Raspberry Pi with Raspbian OS and cgminer 4.6.1 seems to run two Monarchs just fine. CPU load is ~0.40.
If you have a board that is running at 800gh and pulling 570 watts, you are getting close to the limit for the PCIe connectors. To try and cool it off I would recommend trying one or more of the following: 1) more powerful fan on the radiator (stock is ~.33-.5 amp, try to find a 1 amp or bigger) 2) point a fan at the VRM (the space between the pumps) 3) find a cooler location for the unit. I'm curious, are you using BFGminer or CGminer? I know there was talk of commandline underclocking of the units, but I don't know if either program has it implemented as yet.
