[Loadertron]

I recently crossfired 2 radeon 6950 cards on a Crosshair IV formula motherboard and it knocked off the overclock of my cpu from 3.7GHz back to the factory setting 3.2GHz and wouldn't let me overclock again in AMD overdrive so I did it in BIOS. Then last night mid-game the pc died (powered off without warning) I'm guessing overheating but it will not reboot after cooling.

I stripped the system back to the motherboard and PSU and the same problem remains... that is the fans begin to spin but then the power cuts out before the boot sequence can kick in. Can anyone tell me if I've burnt out the motherboard or the PSU? Or if I've damaged the system in some other way?

OS: Win 7 Home
Mobo: Crosshair IV formula
CPU: Phenom II 3.2GHz 6core (black edition) O/C to 3.7GHz
RAM: corsair vengence 16GB
Graphics: 2x Radeon 6950 2GB GDDR5 crossfire (both GPUs O/C from 800MHz to 840MHz)
PSU: Cit 750W 12V
HDD: 2x WD 1TB (no RAID)
Optical drive:2x

If you think you can help but need more info please say so. I'd really like to get this system back up and running. Thanks for reading.

[black-wolf]

Without some parts to test with it's going to be hard to tell. That is a poor quality PSU it probably was only 70% (525w) at best when it was new and they degrade with age. If you can get another PSU to try that would be the first thing. If the PSU failed it could have ruined your mobo and/or other parts.

[Loadertron]

Hi Black-wolf thanks for your reply I have just tried the PSU with another computer and have seen duplicate results so I'm certain you're right, I can only hope now that it hasn't caused further damage.

I guess this is a lesson to anyone building a gaming rig... Don't scrimp on the PSU!

[Skivvywaver]

The PSU is the most important part of the system. You can have the best of everything else but if the PSU won't run it...

[black-wolf]

Corsair and Seasonic make some excellent PSU's. Post what you are planning to buy for us to look at.

[Loadertron]

Sure I'll let you know my plans and if there is still life in the old girl.

[Loadertron]

Looking on amazon saw this but I'm not sure if the wattage is high enough, should I be aiming for a kilowatt... any thoughts?
http://www.amazon.co.uk/Corsair-CMPS...6224337&sr=1-1

[crjdriver]

That should be fine. Here is the amd page showing that pw supply is certified for dual 6950s.
http://support.amd.com/us/certified/....aspx?item=489

If you intend to overclock, you might want to go a little higher in wattage.

[black-wolf]

That should be good and it is 80+ certified.

[Loadertron]

Thanks Crjdriver for the advice and link and Black-wolf for all the advice so far. I think I might back off the overclocking, this pc should be fast enough as it is... I think my enthusiasm had just exceeded my abilities. With the O/C it was benchmarking around 5800-5900 on furmark (about 100fps at 720p and 55fps at 1080p) I'm sure I won't lose much by reverting to factory settings.

I won't mark this as solved just yet until the new PSU appears and hopefully the mobo and other components will come back to life... if not I'll be back asking for more advice.

[Loadertron]

The previously mentioned PSU will take too long to arrive I have chosen another. I think this one should do the job http://www.amazon.co.uk/exec/obidos/..._ya_os_product which will turn up tomorrow. I'll update you on the following success/failure as it happens.

[crjdriver]

Just for future reference, any overclock should be done manually in the bios then checked for stability and temp using prime95 or occt.

Software overclocking or "Automatic" overclocking are worthless IMO.

[Loadertron]

Noted. Do you happen to know if I can undo the overclock by taking out the CMOS battery?

[crjdriver]

Yes, or you can simply clear cmos or as asus calls it RTC. You will have to enter the bios and set any custom settings you need ie sata mode, boot order, hd priority, etc.

[Loadertron]

Well the computer is back in the land of the living. As far as I can tell I have suffered one casuality, I no longer enjoy a triple display set up I seem to be down to two screens. Though the computer detects the monitor it won't display an image, I suppose the obvious solution is to swap the graphics cards over but that means buying an active displayport to DVI converter (on my current primary card it's an active mini displayport to DVI) which is another 20 quid I don't have this month. So that experiment will have to wait. Thanks for all your help, and wish me luck