Hardcore problem i cannot seem to debug

[RejZoR]

Ok, here's the deal. When i put some more load on RAM (Orthos stress RAM test or in SiSoft Sandra), the system just reboots or shuts down. Similar happens sometimes with CPU test. Friend wanted to replace PSU, GFX card and CPU cooler. I've replaced all of them and after that it was time for stability check. And that's where the hell began.

Config:
Intel C2D E6550 + some bad ass Noctua cooler (don't remember the model).
CEON RAM 800MHz CL5 (2GB+1GB)
MSI P35 Neo-F (DDR2 and DDR3 compatible)
Hitachi HDD (weird one that requires SATA+MOLEX power to operate)
Sapphire HD4890 Toxic
CombatPower CP 750W PSU

Tried different BIOS configs including fail safe and optimized default. I've even updated BIOS from 1.0 to 1.70. Nothing changed.

I've tried all sort of RAM configs, i've even tested with 1x 2GB OCZ Platinum DDR3 stick from my system. Still rebooting.

Replaced HD4890 with GeForce 8400GS. Still rebooting.

Re-installed Windows 7. No difference.

Any idea what the reason for this might be? I really ran out of ideas at this point.
It seems very unlikely for CPU to cause problems as i never seen any CPU to do anything like this. PSU is rather "no name" for me, but i think 750W should be decent enough for this regardless. So only thing left is mobo. But i don't have any to test. Is this possible?
Any other idea? This rig is really pissing me off...

 

[Mussels]

PSU and CPU overheating are the two likely ones.


just because it has a big ass cooler on it, doesnt mean its got a good paste application.


Also, "combatpower" is generic - that PSU probably sucks

 

[PaulieG]

PSU and CPU overheating are the two likely ones.


just because it has a big ass cooler on it, doesnt mean its got a good paste application.


Also, "combatpower" is generic - that PSU probably sucks

I have to agree with Mussels here. One or the other is probably overheating.

Only other thing it could be is bad ram. Did you test both sticks independently to make sure one of them isn't bad?

Why the hell would you run a crappy PSU with your system? NEVER cut corners with a PSU. If it dies, it can take the system with it. Your system should start with a quality PSU far before you even decide on a graphics card. Wattage rating means nothing if it's dirty power. Replace that PSU whether it's the cause of your current power or not.

 

[RejZoR]

Noctua doesn't make crappy coolers and i applied the paste. So it's done right for sure. Temperature never goes above 45°C regardless of load (for as much i could load it before it rebooted anyway).

As for the PSU, regardless of how crappy it is, it should run the system easily when i sticked GeForce 8400GS in it. But it didn't. All optic drives and floppy units are unplugged.

EDIT:
Btw, this isn't my system. I'm assembling it for a friend who already bought the components.
I'm using Corsair HX-750. The lowest i ever go is LC Power. They are cheap but still pretty good.

EDIT2:
The cooler is Noctua NH-U12P SE2 in push-pull config. Couldn't get much better than this imo.

So it's down to mobo or PSU.

 

[PaulieG]

Noctua doesn't make crappy coolers and i applied the paste. So it's done right for sure. Temperature never goes above 45°C regardless of load (for as much i could load it before it rebooted anyway).

As for the PSU, regardless of how crappy it is, it should run the system easily when i sticked GeForce 8400GS in it. But it didn't. All optic drives and floppy units are unplugged.

As for the cooler. mussels was just suggesting that the paste was not applied correctly. Obviously, with your temps that's not the issue.

As for the PSU. If it is malfunctioning, it may not matter how much you lighten the load.

What about the RAM? Were your sticks tested individually?

 

[RejZoR]

I've tested each separately in each slot. Even tried with my own 100% tested OCZ Platinum DDR3 stick. But it was still rebooting.

The problem here is that i have no plan on taking my HX-750 from my uATX case. It took me ages to stick it in there. Other one that i have is an old passive PCF 430W generic PSU with just 15A 12 rail (the one that got replaced by this CombatPower thingie). I doubt that thing will be able to support just HD4890 alone, not to mention everything around it.

 

[PaulieG]

I've tested each separately in each slot. Even tried with my own 100% tested OCZ Platinum DDR3 stick. But it was still rebooting.

The problem here is that i have no plan on taking my HX-750 from my uATX case. It took me ages to stick it in there. Other one that i have is an old passive PCF 430W generic PSU with just 15A 12 rail (the one that got replaced by this CombatPower thingie). I doubt that thing will be able to support just HD4890 alone, not to mention everything around it.

Well, if we've ruled out the memory and cpu overheating, I'd say it's the power supply. You most likely need to replace it. Do you have a friend that could let you borrow a decent PSU just to test things? I just cringe at that generic power supply being used with your 4890...

 

[RejZoR]

I'll try to use 430W PSU and disable Aero Glass in Win7 that is installed on this system, to lower GFX card power usage. He'll just have to stick to 2D stuff for now.
He needs the system for some Word editing tommorow, but i just suggested him to send this CombatPower thing back and pick a PSU that i'll sugggest. That should do it i guess.

 

[RejZoR]

I don't know anymore what to think of this rig. I've placed back that old 430W PSU and it seems to hold fine. Tested all CPU benches and no reboot. Tried memory bench. No reboot. Tried Unigine Heaven demo. No reboot. Tried Windows 7 performance index test and it rebooted during disk test.
I have no clue anymore. Now it's either up to mobo or HDD. I don't have either to test so i'm out of options. I'll just recommend him to replace these remaining components just to be sure. I bet there won't be any problems after that. CombatPower PSU will be returned and i'll recommend him something better.