I couldn't get mine to do more than 650KH/s so I put away for a while. Last night I tried again and with any TC over 10240 cgminer starts with error -4 saying it couldn't load the kernel so I was going to flash the BIOS but decided to try different configs first. Now "--thread-concurrency 10240 -g2 --gpu-engine 1050 --gpu-memclock 1650 -I 13" is doing 720KH/s and I think there's room for more tweaking. That's with stock cgminer-3.7.2 so I want to try one of the updates.  Suggestions for which one and any adjustments to config?