Gigabyte Z68 UD7 + i7 2600k = high OC problem

[kamyk155]

Hello and sorry for my bad english.

My computer specification:
- Gigabyte Z68 UD7, i7 2600K, 4x2GB Kingston Genesis 2133MHz, 2xGTX460 SLI, Intel 80GB SSD, Samsung HDDs: 2TB F4EG, 1TB F3, 320GB F4, 850W PSU Silverstone Strider, H2O cooling, SB X-Fi Titanium (in slot raiser X1-X1)

Few days ago I buy new mobo for my i7 2600k - gigabyte Z68 UD7 B3. Before I have asrock p67 fatality and asus p67 deluxe.
I have a problem with high overclocking my cpu (problems when 4,6GHz + OC). With my old asrock fatality I oc my cpu to 4,6GHz with no problem, but when oc some more 4,7-4,9GHz the computer was not stable (dual boot and when come to load windows - stop on black screen with flashing underline). Because the asrock was B2 model - i change it to asus deluxe B3 - problem again the same - OC from 4,7-5GHz = dual boots and freeze on windows loading logo. I was angry so I change asus to new gigabyte z68 ud7 (I think - more expensive mobo = more stable oc).
Now the problem is even more strange - I can oc my cpu to 5,1GHz, enter the windows and stress cpu with all heavy programs (LinX, Prime95) and he is stable even the whole day, but when I turn off computer and power it on again I have dual/triple/quad boot. When the computer finally start - I see normal screen 5,1GHz, RAM and windows start. I can again stress cpu with no problems (no BSOD), play games, do all benchmarks.
I try change all settings in bios. I give mega voltages on Vcore, VTT, ram. Change memory XMP to manual, change mem from 1333 to 2133MHz, turn on/off all energy savers, I change all known OC settings in bios. I take out 1 card, 2 sticks of memory - still nothing. Bios F6, now the F7 beta = still problem. The most strange is that max stable OC on gigabyte is 4,5GHz (asus and asrock = 4,6GHz). On gigabyte 4,6GHz = dual/triple or more boot of computer. I try offset voltages, manual voltages, on/off spread spectrum, llc, change power limits, enable pll - still booting few times after start.....

[Dark Mantis]

Hi and welcome to the Gigabyte Forum.

The issue with the "mulitple booting" is a fairly standard one when overclocking Intel platforms. I can't explain exactly why this occurs but it is very common.

[kamyk155]

I know the dual boot from others mobos but - 3,4,5,6 starts ? My record is 6 times auto on/off and then normal start and enter windows.

[Dark Mantis]

I haven't had the six times but 2 or 3 is common.  It would suggest some sort of instablility there. Are you running the latest BIOS ?

[kamyk155]

Before I use official F6 bios, now beta F7d JZ. No change.

[Dark Mantis]

It's always possible the board/CPU combination just doesn't like going that high.

[kamyk155]

Today I OC my cpu to 5,1GHz and do all benchmarks in windows - no problems with stability.
I use 3DMark 2003/2005/2006/vantage/2011, PCMark7, Heaven 2.5, cinebench 11.5.
After tests I turn off computer and then turn it on again - dual and triple boots........

[Dark Mantis]

Well as I said before this is to be expected. Dual and triple boots are fairly common on overclocked machines. Obviously your system is stable enough so I wouldn't worry about it.