My overclocked computer works but won't start up if its been off for 12+ hours.

Good evening every one, I dont know if this is the right place to ask but I'm having a problem with my computer.. I've been experimenting lately with my computer and over clocking and I've run in to a problem I can't figure out. I've read most of the guides I've found and understand the basics of what I'm doing. When ever I get a decent speed OC going (3.8+ for my i5 760.) I experience problems getting the computer to start up after sitting off for a while.

Last night I used the settings
21x
185 blk
1.3 vcore and 1.3 IMC to get a 3.9 ghz speed
Ram @ 1.5 volts

My idle temps were about ~40

I passed 20 runs of IBT and 5 hours of OCCT where the peak temps I got were 70 degrees on 1 core.

In my opinion this is pretty stable and the PC is running great.


I've always had this problem and thought maybe it was my power supply (which died last night) so I went to replace it with a new corsair TX750 but it still does the same thing. I shut down the computer through windows and left it while I was at work for 10 hours. When I got home and tried to fire it up, the fans and HDDs would spin and the lights would be on for 20-25 seconds but not monitor signal or anything. Then it would turn of for a few seconds and then try again. The only way I can get it to reboot is to reset the cmos and go to default settings. I am able to restart it just fine or leave it off for a little bit and it will start right back up. Its only a long period.

If I do the MOBO's 'preset crazy' OC to like 3.2 it will boot fine. Its only when I get to the 3.8-3.9 range. I didnt know if running 4 sticks of ram was a problem or if one of my settings was wrong.

Anyone have any ideas? I thought it may have been my PSU in the past but its still doing the same thing now with the new one. This seems kind of dumb for a computer that runs otherwise pretty much perfect while OCed. I know I could just leave it on but that's kind of impracticable to not be able to shut it down in case I wanted to move it or lan somewhere.

Here are my specs:
P7P55D-E LX Mobo
i5 760 Cpu
8 Gigs gskill 1600 mhz 4 sticks of 2 gig ram.
Corsair TX-750 PSU v2
2 WD 1 TB HDDs 7200
h50 Cooling
5 case fans

From what I understood from the guides I read was that TJ max from intel was 100 but low 70s was a good number for full load but I may be mistaken. Should I just back off the blck and try to run it at like 3.5? I understood it was pretty easy to run these chips at 4.0-4.2 if you werent on air.

Is there anything I can do about the memory to see if its the problem or the QTT/VTT Voltages? They are on auto.

And just for clarification. Why would it boot and reboot when its been running recently but not if it been off for a long time? Its it because the hardware isnt warmed up or something?

Point taken. Maybe if need to do something like a 3.4 or 3.5 oc and stay conservative. I doubt there is much improvement gaming from those 300 MHz.

I could also upgrade later to a sandy or ivy bridge to get to the 4+ range. Even then will there be a huge difference from my 760 3.5 to a 2500k at 4.2 for gaming?