user10088: I built the following rig:
5x SAPPHIRE TRI-X R9 280X 3GB GDDR5 OC (UEFI)
1x AeroCool Templarius Imperator 1150W 80 Plus Gold
1x HighPower Tech 1200w Gold Plus (HP-1200-G14C-GOLD)
1x Gigabyte GA-990FXA-UD3 motherboard
1x W.D Caviar Green 500GB SATA III HDD
1x Kingston KHX1600C9D3B1/4G
2x Unpowered risers 1x 16x
3x Powered risers 1x 16x
I have the templarius PSU powering the motherboard, the HDD and 2x GPUs with unpowered risers.
The other 3 gpus are powered by the 1200w PSU and connected to the powered usb risers.
I Installed Windows 8.1 and plugged one gpu. It automatically installed the Radeon HD 7990 driver. Then connected the second gpu and followed the same process with the other gpus.
I then executed cgminer and everything looks stable at 740Khs each.
However 1h later the rig shuts down. It always shuts down aprox. 1h later..
Regards,

user14359: My brothers machine was doing this also. We fixed it by pulling a card. The motherboard was pulling too much power under load. 

10088: <p>I built the following rig:</p>

<p>5x SAPPHIRE TRI-X R9 280X 3GB GDDR5 OC (UEFI)
1x AeroCool Templarius Imperator 1150W 80 Plus Gold
1x HighPower Tech 1200w Gold Plus (HP-1200-G14C-GOLD)
1x Gigabyte GA-990FXA-UD3 motherboard
1x W.D Caviar Green 500GB SATA III HDD
1x Kingston KHX1600C9D3B1/4G
2x Unpowered risers 1x 16x
3x Powered risers 1x 16x</p>

<p>I have the templarius PSU powering the motherboard, the HDD and 2x GPUs with unpowered risers.
The other 3 gpus are powered by the 1200w PSU and connected to the powered usb risers.</p>

<p>I Installed Windows 8.1 and plugged one gpu. It automatically installed the Radeon HD 7990 driver. Then connected the second gpu and followed the same process with the other gpus.</p>

<p>I then executed cgminer and everything looks stable at 740Khs each.</p>

<p>However 1h later the rig shuts down. It always shuts down aprox. 1h later..</p>

<p>Regards,</p>
 14359: <p>My brothers machine was doing this also. We fixed it by pulling a card. The motherboard was pulling too much power under load. </p>
