Re: Q6600 ; Hitting a wall at 2.85Ghz, no voltage helps.
#1 - it's likely your motherboard. Although it is called a "680i" LT, it is not the same exact chip as the 680i in a board with less features. Many just wont OC for crap.
#2- a more powerful power supply might help as well. Before my son spilled soda on it, I had no problems hitting 3.6GHz with my 700w OCZ. While waiting for a new power supply I ran with an Ultra 550w power supply and couldn't keep it stable @ 3.2 GHz. Now that I'm back to a good power supply I can run 3.6 stable again.
MSI MPower Z87 | 4770k | CNPS9900MAX-B | 8GB G.Skill 1866 | EVGA GTX760 |ThermalTake 850w | X-Fi Titanium | HAF | Asus PA248Q | Lycosa | Death Adder | Win8 Pro 64
MSI GD65 | 2500k | H50 | 8GB G.skill | GTX570 | Ubuntu 13.10
17" Inspiron | i5 | 4GB DDR3 | 500GB HDD | Win7 Pro 64