I've installed ubuntu on an old laptop. It was, as expected, a piece of cake, following the directions on page 1. I didn't do anything else after building cgminer.
However, I get exactly the same results. Sounds like a bad device. I assume there isn't any additional tools I can use to see if it's something else.
I got my new R606, plugged it into my new ubuntu install on my laptop, and WHAM, running at 781GB with just the defaults.
Next question: I believe after reading the posts that the current version of cgminer autotunes. Does that mean I just need to increase the vCore using the buttons on the R606 to increase the rate? Or do I need to use the settings for cgminer to set the frequency? Or both?