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.

Thanks for your insights in advance.

 

[cadaveca]

1. top slot is x16 link, bottom is either x8 or x4. Anyway, you say temps are higher, but those are reasonable temps either way.


2. Dual fan, becuase it's quieter, and cooler running. Although a reference card taht exhausts out the rear may be useful too.


3. my bottom card is always coller than the top card, due to utilization, so put your hottest-running card in the bottom slot.

 

[yangwangbrock]

1. top slot is x16 link, bottom is either x8 or x4. Anyway, you say temps are higher, but those are reasonable temps either way.


2. Dual fan, becuase it's quieter, and cooler running. Although a reference card taht exhausts out the rear may be useful too.


3. my bottom card is always coller than the top card, due to utilization, so put your hottest-running card in the bottom slot.

Thanks for your reply. I thought for maximus extreme - Z all 4 slots are 16 so it wouldn't matter which you use it runs at 16? I could very well be wrong.

 

[badtaylorx]

no they run at x8 if you have more than one

(worst part of the sandy bridge)

unless you run tri-fire...than its 8-16-16

this is done because the nf200 chip that adds lanes also adds latency

x8-x8 is actually faster than x16-x16 w/nf200 because of it

 

[yangwangbrock]

Returned my Asus Direct CU II last night got 2 x MSI 6970 Lightning Frozr 3 in CF. Couldn't be happier. MSI does a much better job at cooling than the supposed better Asus Direct CU II.

 

[Wrigleyvillain]

3. my bottom card is always coller than the top card, due to utilization, so put your hottest-running card in the bottom slot.

Wait isn't it the other way around? The top card is the primary and thus has the greater utilization.

Or maybe he has a non-traditional layout I'm missing...

 

[yangwangbrock]

Wait isn't it the other way around? The top card is the primary and thus has the greater utilization.

Or maybe he has a non-traditional layout I'm missing...

I cannot tell which one is which...I just assumed the top card is the hotter one, as it does not have as good air flow as the bottom card.

 

[cadaveca]

Wait isn't it the other way around? The top card is the primary and thus has the greater utilization.

Or maybe he has a non-traditional layout I'm missing...

No, i meant exactly what I said...the top card gets used the most, so which ever card runs hottest in that position should be moved to the lower slot.


IE, card a runs 90c in top slot, card b runs 95c in top slot, then card b should be put in bottom slot.

It could be just down to airflow, but both my cards run identical temps when placed in the top slot, and in the bottom slot, so it's hard for me to tell. I have noticed, however, that the bottom card doesn't get 100% loading as often as the top card does.

 

[yangwangbrock]

No, i meant exactly what I said...the top card gets used the most, so which ever card runs hottest in that position should be moved to the lower slot.


IE, card a runs 90c in top slot, card b runs 95c in top slot, then card b should be put in bottom slot.

It could be just down to airflow, but both my cards run identical temps when placed in the top slot, and in the bottom slot, so it's hard for me to tell. I have noticed, however, that the bottom card doesn't get 100% loading as often as the top card does.

For my new CF set up both cards get 99% (never 100%, not sure why) quite often according to Afterburner.

One question Cadaveca, does it matter which card i connect my triple monitors to? Like if I connect my monitors to the top card, does it make it run hotter? If I connect the monitors to the bottom card, does it make the top card run cooler? I have my monitors connected to the top card at the moment. My top card idles around 50 and highest it goes to around 79. The bottom card idles around 35 and full load at 70. I am assuming the bottom card runs cooler, as again I don't know which is which.

 

[cadaveca]

the card with the monitors generally runs a bit hotter, as it sits under use at desktop, while the slave card is fully powered down by PowerPlay.

However, if you use the other card for monitor connection, you will not have any image in BIOS or while the OS loads, unless you BIOS supports setting the other slots are the "primary boot device".