CRash when I run setx GPU_MAX_ALLOC_PERCENT 100

[phaddie]

Hey guys,

  Been mining for a few days with my new R9 290.  Just now I was playing with settings trying to get the most Kh/s out of it.  I decided to pump the memory clock up a bit (from 1500 - 1750) and when I did that my screen went blank.  No reboot or anything just a blank screen.

  Since I was doing the changes from within cgminer my old working settings were in my .conf file so I rebooted.  Now when I run CGMiner my system goes to a blank screen when my bat file runs setx GPU_MAX_ALLOC_PERCENT 100.

  Did I somehow fry the memory on the card and if so how do I test this before I send it back?

  Any help would be good, thank you in advance

   Phad