I've just finished the overclock of my new sandybridge system. I ran prime 95 for 10 hours and the overclock is super stable, so I thought I would share the exact steps of how I did it with those of you who own a 2500K (it probably would work same on the 2600K) and a Gigabyte GA-P67A-UD4 Mobo (I assume this is a fairly common combo for those of you who like to use the OC potential of your unlocked 2500K CPU). Prior to my OC attempt I've read many other guides and tried them all but non worked as stable as what I did even though I followed them exactly. My OC is also the most simple of them all and works rock solid with the power saving options on (in all the guides I've seen the EIST and C1E were disabled). So here it is:
enter M.I.T. and then the advanced frequency settings:
here leave the CPU clock ratio @ default (33x for 2500K), I did not touch the BCLK and chose profile1 for the memory. Bios set my memory to 1600 by default but it is capable of 2133Mhz, so I just chose the SPD profile of my RAM. In case your memory's SPD isn't read properly, you can adjust it manually in the memory menu.
next, enter the Advanced CPU core features and leave the CPU clock ratio @ default (33x), change the turbo ratio value for each core to 47 and raise the turbo power limit to 200W. leave everything else @ auto.
next, in M.I.T enter the Advanced voltage settings and enable load-line calibration. change the CPU Vcore to 1.425V. I left everything else on auto again.
thats all. The OC is rock solid, you still have all the power saving features on but will have the OC WHEN you need it.
BTW, all this resulted in 4.7Ghz (exactly 4689Mhz). CPU-Z shows 1.404V because of V-drop. I know this isn't top OC, since sandybridge is said to reach 5Ghz but I feel that having air cooling, this is a safe and to me a satisfactory OC, that I can use 24/7.

Main rig: NZXT Phantom modded case with Danger Den WC, MSI Tomahawk B350, Ryzen 1700X @ 3.4Ghz, 16GB Patriot Viper DDR4 3200Mhz 16-18-18-36, MSI GTX 1060 3GT OC, Asus 24" 1ms 144hz, Intel P7600 256Gb nvme PCiE, Samsung 2TB; PC P&C 750W, Win10 Pro 64
Laptop: Dell XPS 1530 (T9500; 4GB 800 RAM; 120GB Crucial SSD; 8600GT; WIN7 64bit)
my complete GFX tuneup & cooling mod: http://forums.legitreviews.com/viewtopi ... highlight=