HD 6970 Crossfire Questions

[yangwangbrock]

Hi,

I am considering adding another HD 6970 to my rig. Here is my configuration:

Corsair Obsidian 800D
I7 2600K OC to 4.6GHZ
Noctua NH-D14 CPU Cooler
Asus Maximus Extreme - Z
Corsair Vengeance 4 x 4 gb kit 1688 LP
Corsair AX 1200 Gold Standard
Crucial 128 GB SSD
WD Black Cavier 1 TB
Asus HD 6970 Direct CU II

I have also added 3 120mm Noctua fans at the top of the case as exhaust fans, as well as replaced all stocking 140 mm fans to Noisebreaker PK-3.

Here are my questions:

1. When I insert the graphic card into the first PCI-E slot (the one closest to CPU), it runs really hot: 50 at idle and 80+ at full load. While I use the 2nd PCI-E slot, it runs quite normal (idle at around 40 and never goes over 60 at full load). Does anyone know why this is? I would have imagined better air flow with the card being installed at the first PCI-E slot, as it gives more space for air flow (800D has a 140 mm fan as main air intake at the bottom).

2. As Asus HD 6970 Direct CU II takes 3 expansion slots, I will have to pick up another 2 slot version of HD 6970 as I am running out of space. I am eyeing at 2 options: Asus EAH HD 6970 2 GB reference version, or Sapphire HD 6970 dual fan edition. Which one would you guys recommend and why?

3. Further to the 2 questions above, I am thinking installing the 2 slot HD 6970 at the top PCI-E slot, and install Asus 6970 DCU II at the 3rd PCI-E slot. The reason that I do not use the 4th PCI-E slot is because it litterally leaves no space between the GPU and the metal that divides the MB department and PSU. So that leaves only one slot between the 2 GPUs. Would that be sufficient for cooling? I am not looking into water cooling at all.

This is my first time posting here. been a long time lurker on this site. Thanks for your insights in advance.

 

[alrobichaud]

1. I have an xfx 6970, sapphire 6970, powercolor 6990 and all three run at typically 85 under full load. I would not worry too much about the temp. I can't see how moving the card 2" closer to an intake fan would make much of a difference at all let alone 20 degrees.

2. I like having my gpu's exhaust externally so I would go with the ASUS gpu. Does the sapphire run any cooler with dual fans exhausting in the case as opposed to a
blower exhausting out the rear? Don't know since I have never owned one.

3. A two slot space is enough for cooling. I have run all 3 of my cards side by side with small rubber spacers to allow for air more air flow and they did not run any hotter than when I had two cards separated by a pci-e slot. The fans needed to work a bit harder but that is all. They still ran below 45% at the worst so it really wasn't any louder. Also, I have not looked up your motherboard but if it is like mine the slot configuration is probably 16/0/0/0 16/0/16/0 16/8/8/0 8/8/8/8. Any configuration other than this and both cards will probably not work. So I think you definately want to use slot 1 and 3.

 

[yangwangbrock]

1. I have an xfx 6970, sapphire 6970, powercolor 6990 and all three run at typically 85 under full load. I would not worry too much about the temp. I can't see how moving the card 2" closer to an intake fan would make much of a difference at all let alone 20 degrees.

2. I like having my gpu's exhaust externally so I would go with the ASUS gpu. Does the sapphire run any cooler with dual fans exhausting in the case as opposed to a
blower exhausting out the rear? Don't know since I have never owned one.

3. A two slot space is enough for cooling. I have run all 3 of my cards side by side with small rubber spacers to allow for air more air flow and they did not run any hotter than when I had two cards separated by a pci-e slot. The fans needed to work a bit harder but that is all. They still ran below 45% at the worst so it really wasn't any louder. Also, I have not looked up your motherboard but if it is like mine the slot configuration is probably 16/0/0/0 16/0/16/0 16/8/8/0 8/8/8/8. Any configuration other than this and both cards will probably not work. So I think you definately want to use slot 1 and 3.

Thanks Alrobichaud for your quick reply.

1. Beats me. It is actually 2 inch away from the intake fan, right beneath the CPU cooler, which is positioned horizontally so i don't think the GPU gets any heat from the CPU cooler. So yeah not sure why the 20 degree difference.

2. Thanks for the recommendation. Sapphire claims it runs cooler than reference card but that is yet to be proven.

3. I thought my MB has 4 PCIE x 16 slots so it wouldn't matter which slot you use it would be running at 16? I could very well be wrong. But yeah 1 slot is better than your back to back setting I guess

 

[alrobichaud]

Just looked up your board. Guess I should have done that before opening my mouth. It is kind of a strange set up but here is what you can do.

4 x PCIe 2.0 x16 (x16 or dual x8 or x8, x16, x16)

I think you should go with the stock ASUS card to exhaust the air out of the case and put the direct cu ii in the botton slot above the air intake. If you are using an air cooler do you really want another 85 degree card exhausting inside your case.

 

[yangwangbrock]

Just looked up your board. Guess I should have done that before opening my mouth. It is kind of a strange set up but here is what you can do.

4 x PCIe 2.0 x16 (x16 or dual x8 or x8, x16, x16)

I think you should go with the stock ASUS card to exhaust the air out of the case and put the direct cu ii in the botton slot above the air intake. If you are using an air cooler do you really want another 85 degree card exhausting inside your case.

Thanks. Would all stock reference card exhaust out of the case? for example would an xfx or sapphire stock reference card exhaust via rear?

 

[alrobichaud]

Yes. Even with good airflow two 85 degree gpu's exhausting inside the case is a lot of heat IMO. Unless you have lot's of cooling fans and a case with a fairly open top and/or top mount exhaust fan. By lot's of cooling fans I mean either 4 side mount 120mm or a single 240mm plus front rear and top mount fans.

 

[yangwangbrock]

Best answer selected by yangwangbrock.

 

[Mousemonkey]

This topic has been closed by Mousemonkey