PC loses power during boot after any change to cpu FSB???

**metheds21** · July 4th, 2011, 12:55 AM

Ok Im grasping at straws here I'm not and expert overclocker by any means but I build my own PC's and what I do is buy midrange stuff and push it to its maximum clock speeds

Well my problem is I just built myself a new pc and and ive been using it for a few days (testing) and I thought I'd tweak my FSB on my intel i5 core 2500k sandybridge, sadly when ever I change the FSB no matter what I change it to even to 3.32gz (stock is 3.30) My pc doesn't hang when it boots it totaly loses power!!(and IMO a tiny fsb change shouldn't require a voltage increase) After about 15seconds it restarts it self and never gets past the post screen before it loses power again.

Now heres the part thats got me confused I get back into the bios, change the FSB back and it still loses power on boot??? so I have to load failsafe defaults and then it works again......

Anyways heres a few things i think it could be:

#1 CPU/bios protection kicking in

#2 voltage to low (but i mean cmon it still does this at stock speeds)

#3 PSU my psu is old, its from my last PC and i've had it for about 5 years also the wattage and 12v rail amps are not very far above the minium for my specs (ill post specs below)

#4 and the worst possibilty so far, defective parts It's not to late to RMA anything back to new egg so if anyone has any ideas lemme know.

SYSTEM SPECS
Windows 7 home premium
Gigabyte z68xp-udp3 Mobo
Intel i5-core 2500k 4 cores @ 3.30ghz sandybridge (3.7ghz turbo boost)
8 GB (2x4gb) pc14900 Gskill ram
Crucial 120gb SSD SATA 6gb/sec (windows 7 installed here)
Western digital caviar 1TB secondary HD 7200rpm sata 6/gbsec
Galaxy Nvidia GTX465 video card requiring a 550w PSU with 38amps on the 12v rails
PSU 600w XION with two 12v rails 22amps each (psu is pushing 5 years old)

Everything but the psu is new, but im starting to think its not the psu I have ZERO problems when I leave the FSB of the CPU alone, and I've done ALOT of overclocking on my own pc and others, spending days pushing clock speeds to the max, and I seen plenty of hangs and blue screens but never total power loss......

ANY help would be greatly appreicated sorry for the long post and the horrible spelling

**stroyal** · July 4th, 2011, 09:58 AM

You said yourself it requires 550 watts with 38amps, that's because a real 550wat power supply will have in the range of 38amps 12v.
Edit
Sorry,I didn't see the 2-12v rails, what is the total combined 12v watts?
I still suspect the power supply, because of the instant shutdown and the reset.

Newegg.com - XIGMATEK ACXTNRP-PC602 600W ATX12V Ver.2.3 SLI Ready CrossFire Ready 80 PLUS BRONZE Certified Active PFC Power Supply

Newegg.com - CORSAIR Builder Series CX600 V2 600W ATX12V v2.3 80 PLUS Certified Active PFC Power Supply

Newegg.com - ENERMAX NAXN ENP550AWT 550W ATX12V Active PFC Power Supply

even this 520w has 40amps.
Newegg.com - Antec NEO ECO 520C 520W Continuous Power ATX12V v2.3 / EPS12V 80 PLUS Certified Active PFC Power Supply

Instant power loss with a auto reset, sounds like the circuit breaker, inside the power supply, to me.

**stroyal** · July 4th, 2011, 10:57 AM

Is this it?
Newegg.com - XION PowerReal XON-600F14T-201 600W ATX12V SLI Ready Power Supply

It only has 570 watts available for the 3.3v, 5v,and both 12v, rails combined, according to the label.

The 2-12v rails are 528watts combined, and the 3.3v. and the 5v are 380watts combined.
That adds up to 908watts, that could potential be sharing 570 watts.

The actual circuitry could be different, but you can't tell from the poor label.

**metheds21** · July 5th, 2011, 07:03 AM

I think you have it there, newegg is down so I can't look to make sure.

And ya I thought it was the psu but I just find it odd that I don't have any issues unless I change the clock speed, I must really have to be on the edge and the fact that the voltage to the CPU changes under normal operation you'd think that would trip it if it went too high also. I can run prime 95 and 3dmark no problems.

But I'll try putting my old video card back in(geforce 8600) and removing the gtx465 and try overclocking the cpu then.

Ill be back with the results after some sleep just worked a 12 hour night shift on the fing 4th of july ugh.

EDIT : The newegg page finally loaded that is my PSU.

**stroyal** · July 5th, 2011, 08:38 AM

Good Idea, it is hard to say for sure. without testing.

Don't forget, when any electrical device starts, it draws much more power than when it is running full load.

Some, like large motors, draw, more than triple.
Any overclock, may add exponentially, to the start up surge, in a computer.

A good power supply, that size would not dedicate more than 50watts, to the 3.3, and 5v combined, in order to get the 12v rail where it should be, for a modern computer, that mostly uses 12volt.

**JPMiller** · July 5th, 2011, 01:42 PM

I'm less inclined to believe its a PSU issue, and more inclined to believe its a mobo issue.
Do you have the latest Bios?

**metheds21** · July 7th, 2011, 08:39 PM

updated bios, but i haven't had time to do anything else yet.

But I have some good news, I disabled Intel turbo boost in the bios and the instant power loses have stopped current clock @ 3.43ghz up from 3.30 and before I couldn't make any changes to the FSB

I've never delt with intel turbo boost before but to be honest I'm surprised that a tiny fsb change would do this.
and I didn't try disabling any CPU features because In the past I haven't had to unless I'm pushing much higher then stock speeds.

I may have just gotten lucky, like I said I haven't had any time to really test, I'll see If I can figure it out over the weekend.