I got a U3 for Christmas and after tinkering for a few hours under the tree yesterday, it's happily hashing at ~56GH/s. I settled on an RPi running the cgminer build from the most recent Minera img. I let it run overnight and there doesn't seem to be any major issues. However, there are a few specific questions I have that I wasn't able to dig up answers for.

1. Has anyone come up with some general thresholds (safety/stability) for the voltage and frequency settings? I'm messing around with the stock equipment until I can integrate into my mining rig back at school.

2. Is there any way to forces PWM values to the fan controller? The fan runs at a sluggish RPM and I'm past the point of letting miner fans bother me. I'd prefer to crank it up and cool things down.

3. What causes the fluctuation of the hash rate? Over a 15 minute period, it'll bounce around the 35-70GH/s range. I see the same thing with my big rig, but I've never looking into the cause.

Thanks!