Having issues with sgminer and windows 7 crashing or freezing a few hours after running with intensity setting over 15 with 3x R9 270 (non x), no issues with cgminer previously, I could run it for weeks mining dogecoin. (windows 7, 13.12 catalyst)
sgminer will run fine at 14 intensity at basic settings like below but I only get about 1.2 to 1.3 MH per card
sgminer.exe -k x11mod -I 14 --gpu-engine 1050 --gpu-memclock 1250 -o stratum+tcp://drkpool.com:3333
I couple things you can try:
1. lower the --gpu-engine and see if that helps.
2. Use the "print" function on this thread and then ctrl+F and enter "270". See what other 270 users are using for settings
3. Be sure to disable and then enable the video cards after they crash. do that in device manager. Or you can do a full restart but sometime it's better to disable/enable
When I had your symptoms I got it working by changing memclock or adjusting Intensity.