Gigabyte Mboard, 2 7970, want to do 4

[Spendulus]

So this rig

• Windows 7, now running Ubunto 12.04
• Gigabyte AMD Radeon HD 7970 OC 3GB GDDR5 DVI-I/HDMI/2x Mini-Displayport PCI-E 3.0 Graphics Card GV-R797OC-3GD
• MSI V2 Socket AM3+/AMD 990FX/DDR3/CrossFireX and 3-way SLI/SATA3 and USB 3.0/A and GbE/ATX Motherboard 990FXA-GD80 V2
• AMD FX-8350 FX-Series Eight-Core
• Power supply TR2 RX 1200W
• Antec Kuhler H2O 620 Liquid CPU Cooler System

Is happy running 2 7970.  If I add a third, the fans on the third do not run.  Does not seem to matter if I

• use one or another of the slots
• use an extender, with or without powering the molex
• use a 100 ohm resister to fake out a display attached
• use a 2nd power supply for the 3rd test card

Basically the fans should be running after the POST startup, so I do not think it matters whether Windows or Linux at this point.

What to do?  How do I run four cards, or maybe it can't be done?

[frojoe]

Does the computer recognize the card? Have you tired to put a load to the card?

[Spendulus]

Does the computer recognize the card? Have you tired to put a load to the card?

Because the fans never turn on, it seems that the computer does not recognize the card.

That actually is the issue.

[frojoe]

Ah. I had the issue were the fan wouldn't spin because the ulps setting needed to be disabled. Its some power saving mode and the card doesn't look like its works but the computer see it. That was my case. If it put a load to the card the fan you start to spin. Since your rig does recognize the 3rd card in devices I would put the 3rd card in the 2nd card slot and see if it works. That will have you narrow down the issue

[Spendulus]

Ah. I had the issue were the fan wouldn't spin because the ulps setting needed to be disabled. Its some power saving mode and the card doesn't look like its works but the computer see it. That was my case. If it put a load to the card the fan you start to spin. Since your rig does recognize the 3rd card in devices I would put the 3rd card in the 2nd card slot and see if it works. That will have you narrow down the issue

Ulps is a registry setting.  I don't think it exists in linux, but regardless, the 3rd card does not spin up before the operating system is loaded.  I believe all the cards should power on when they are recognized by the motherboard POST, right?

[xide]

few questions for you when you power your rig is third card fan working or not?
how is connected to psu?with 1x8pin and 1x6pin pci e or molex adapters?
did you checked solo that card is working fan and card ?