2500k overclock voltage help

Any help?

The core voltage reading in CPU-Z is the one that you should watch, along with the max temps. Although, I think it is odd that core voltage shows only 1.056v during a Prime95 run at 4.3GHz. Are you sure that you are reading it as Prime95 is running, while all the cores are at 100% load? If you left the voltage on auto and just changed the multiplier, you should be getting around 1.35v and possibly more at 4.3GHz.

Yeah, I am definitely running it when Prime is on. I have tried starting CPU-z both before and after running prime and it makes no difference.

I have the exact same problem with the exact same processor and motherboard! Gigabyte Z68XP-UD3/2500k. This is also not my first Z68/2500k setup. My last 2500k would go to 4.5Ghz fully stable on stock voltage with an Asus board and if my memory is accurate it showed about 1.25v in CPU-Z during prime95 tests. Mine does not go over 1.056v and becomes unstable after about 45 minutes even at 4.3Ghz which leads me to believe it's possible that the CPU-Z reading is accurate. If the CPU were getting 1.25V there's no way I'd be having problems at 4.3Ghz when my last one would go over 4.5Ghz easy.  
I've tried setting the voltage manually and even using templates of known good mild overclocks from guides (which I never used or needed previously).
Does anyone know of any bugs or issues with these boards? I'm running the latest BIOS (F10), maybe an older BIOS version wouldn't have this issue? My next step will be contacting Gigabyte for an RMA if the problem persists and no one comes up with a fix for it. Thanks in advance.

EDIT:: It looks like Coretemp is actually showing the correct voltage of around 1.25V and the temps appear to be more accurate as well. I may have jumped the gun thinking this was a mobo issue when it's probably just a bug in CPU-Z. The main problem still remains that I can't really run Prime95 on anything higher than 4.3 without a hardware failure message. Same goes for gaming, 4.3 is great... 4.4 results in things getting quirky after a while. Exact same problem OP is having. I am going to start from scratch using only Coretemp and see if I can figure out what the deal is and I will report back with any helpful findings. All ideas and suggestions are more than welcome.

Ljgrimm, what cooler are you running?

I use RealTemp to monitor my temps and Vc. That program was updated to work well with the SB CPUs.

You should have something like LLC (load line calibration) in BIOS with several settings available to you. Thou I use an Asrock M/BD all of them should have some method of reducing Vdroop when your CPU is under load.

I have to use 1.335 Vc for stability with SLI 480s @ 4.5GHz.

Also you may have to set your ram to 1333 for that OC. Some M/BDs handle higher ram speeds than others.

After doing some more research and troubleshooting I have come to find it's an issue that some Gigabyte boards have from the factory. Thanks for the suggestions but I've exhausted all possibilities and it turns out the Vcore reading was false from CPU-Z, I was actually getting about 1.36v which is plenty for what I'm trying to accomplish. Also my RAM is kept at stock frequency and timings at all times to rule out any variables. The real issue is that it won't run stable under load at 4.4 without running the vcore way too high and it won't even post at 4.5Ghz no matter what I do. If there were nothing wrong with the board it would at least post, get to the desktop and THEN fail due to prime95 or some other stress test telling me I'm pushing things too far. A no-post at 4.5Ghz regardless of settings is just not normal. I have thought about contacting Gigabyte for a replacement but it's just not worth the down time. If I run it at 4.3 or lower all is well, temps are good, prime95 passes fine and performance is great. I think I'm just going to set it at 4Ghz and call it a day. That is still more than enough to destroy anything in its path. It seems to really like the GTX480 as well. I beat the average GTX680 score by nearly 500 points on passmark (4,028 vs. 4,510) with a mere +100Mhz overclock on the core and +152Mhz on the memory. OP, it looks like we got dud Z68 boards. You can take a week or two off for an RMA or be happy around 4Ghz. Good luck to you.

Passmark run, just for kicks.