Funny you post this now. I just rebooted my iMac after my first go at O/C:ing ever...in small 10Hz increments.
When I hit Apply the monitor showed blue/white stripes all over and computer locked. YIKES!!
I hardbooted and everything seems fine. *pheww*
Well, learning by doing wrong. I'm not gonna stop. Computer is very cool on stock settings so gonna read in some more and then try again.
However, I will NOT touch the voltage, just core and mem clock.
Knowing I have perhaps 10 more frames luring in my card drives me.