Core i7 voltage goes down when stressed

Hi everyone as the thread name says my core i7 920 OC to 3.5ish GHZ 166mhzx20 plus turbo core voltage goes down when its stressed. According to CPU-Z at idle, the voltage is at 1.264V when i stress the CPU with Intel Burn Test v2.1 with 8 threads and standard memory, cpu-z reads a voltage of 1.232. I thought the voltage should be going up not down! This has been giving me problems when i wanted to overclock to a higher frequency it would boot up fine and when i stress the cpu the voltage would go down and cause instability. My motherboard is the Gigabyte ex58-Ud3r, antec 650 watt psu. If anyone has some tips i could try to try and fix this problem or knows a solution i would be very happy to hear it! If you need more info on the rig please ask. Thank you in advance!

I can help. Go into BIOS, in the MB Intelligent Tweaker (M.I.T.) menu slide to the bottom and enable "Load-Line Calibration"

Hi Crashman I actually tried this but the voltage still goes down when the CPU is being stressed. I really appreciate your input though

EDIT: Actually i noticed that the voltage didnt go down as much with the load-line calibration enabled. Instead of a .05 volt drop its a .02 voltage drop which isnt really much. I think thats good enough for me.