This system was very stable and worked well until I did a stupid thing.
Last week I saw Gigabyte had a F12 bios and I was running on F9e, so I upgraded the bios. The upgrade went fine, but of course it deleted all my user bios settings - so I had to do them all again and yes I had not written them down - stupid I know.
So I start trying to overclock back to my previuos settings, and I am really struggling. Everytime I try to overclock the RAM to 1600 the machine will only see 2Gb or 4Gb when booting no matter what voltages applied.
Eventually I bought some new Corsair TR3X6G1600C9G Ram and now I can get the RAM overclocked to 1800 easily.
However, starting to OC from 2.66Ghz I can get to 3.2Ghz ok, but will struggle for 1 hour to get 4.00Ghz. Once I have the 4.00 I can boot Windows and run burn tests and play games ok.
But once the computer is cold those saved OC settings will fail to post, so I have to reset BIOS again, then nothing above 3.2Ghz will post until the system is warm again and then I can run 4.0Ghz again.
I have tried all manner of voltages low and high, and even if I get the PC to boot at 4.00, it will not post when cold.
What is the problem is it CPU, Motherboard or even PSU - I have a 1000W PSU in this computer.
I have even tried the old BIOS I was on and that changed nothing.
I have tried contacting Gigabyte and they have not even answered my message and I really do not have the money to buy a new CPU and Mother board to find the problem
Is that 4.0ghz OC actually stable as in you did 12 hr Prime95, 1 instance for each thread, and no errors came up?
It could also just be a bad connection somewhere, that one things heat up and expands slightly becomes a good connection.
Only thing I can suggest in that case is to check all connections to make sure they are good, and then start eliminating components 1 by 1 via testing them in another system, or swapping in a known good one to your current system.