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Crossfire ASUS HD7970-DC2T-3GD5

post #1 of 8
Thread Starter 
in order to improve frame rates in FPS games like BF4,
I'm contemplating buying a second "ASUS HD7970-DC2T-3GD5" to put in crossfire with my existing card (same brand and type).
I'm using a "ASUS P8Z77-V PRO" main board with a sufficient large PSU.
I've always stayed clear of SLI and Crossfire solutions, but I'm tempted now as prices for 7970 are dropping.

Anyone who has tested or can predict the performance / frame rate improvement of this setup when gaming at 1920x1080? And at 2560x1440?
I'm sure it's not 200% biggrin.gif, but how much can I expect: 150%? less?

thanks!
post #2 of 8
I had two Asus HD7950 DC2 TOP V2 cards (cooler is 100% identical to HD7970 DC2 model).

You can expect up to 180% performance , not more in real usage (gaming).

Also those coolers are 2.5 slot , that means space between top and bottom card is ~ 0.5 inches, that will cause top placed card to run ~ 10 - 12C hotter than botom card.

In my case slightly OC'd cards @ 1000/1575MHz (stock voltages), top card ran ~ 74C with 54% fan speed, bottom card ran ~ 60C with 35% fan speed. (I had set up custom fam profiles in MSI Afterburner).

Now with your HD7970 DC2 you can expect even higher temps as your GPU runs at higher voltage (my stock Vcore was 1.094V).

For pics of my rig check out my signature rig.

Personally I would never come back to CF, I have sold one of my cards, BF3 and BF4 did not run wery well, GPU usage was ~ 70% on both cards (stock freq 900/1250MHz) and with i7 3770K @ 4.5GHz.

I had huge FPS drops from 140FPS to ~ 65 which really hurts gameplay experience.

Now I run one HD7950 @ 1150/1600MHz, gameplay is much smoother than with two cards in CF, even though Avg frames are lower, min FPS is much more stable.

Crysis 3 ran fine with CF, no problems there.


CHEERS..
     
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post #3 of 8
Quote:
Originally Posted by KingT View Post

I had two Asus HD7950 DC2 TOP V2 cards (cooler is 100% identical to HD7970 DC2 model).

You can expect up to 180% performance , not more in real usage (gaming).

Also those coolers are 2.5 slot , that means space between top and bottom card is ~ 0.5 inches, that will cause top placed card to run ~ 10 - 12C hotter than botom card.

In my case slightly OC'd cards @ 1000/1575MHz (stock voltages), top card ran ~ 74C with 54% fan speed, bottom card ran ~ 60C with 35% fan speed. (I had set up custom fam profiles in MSI Afterburner).

Now with your HD7970 DC2 you can expect even higher temps as your GPU runs at higher voltage (my stock Vcore was 1.094V).

For pics of my rig check out my signature rig.

Personally I would never come back to CF, I have sold one of my cards, BF3 and BF4 did not run wery well, GPU usage was ~ 70% on both cards (stock freq 900/1250MHz) and with i7 3770K @ 4.5GHz.

I had huge FPS drops from 140FPS to ~ 65 which really hurts gameplay experience.

Now I run one HD7950 @ 1150/1600MHz, gameplay is much smoother than with two cards in CF, even though Avg frames are lower, min FPS is much more stable.

Crysis 3 ran fine with CF, no problems there.


CHEERS..

i only played 1080 using crossfire (7950/7970) with an i7 SB @4.5 and my minimum never dipped below 75 in BF3 MP 64 with the gpus at stock. my usage on both never went below 90%.
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post #4 of 8
Thread Starter 
tnx for the answers!

it is actually the "Top" version I have (ASUS HD7970-DC2T-3GD5).
Mine is stable under gaming conditions at 1100/1500 (air) and cpu is a 3550K @ 4.5-4.7 (depending on summer/winter, "liquid" Corsair H100 smile.gif). Temps are around 70C for the gpu and 60C for the cpu.

I have played with both Asus' own program and of course Trixx to overlock the gpu; memory temps are a problem and more speed results in artifacts.

I want constant 120+ fps which currently is only possible with medium settings in BF4, but I would like more quality.
180% performance improvement in Crossfire is more than I could dream of but unstable fps just does not do it for me either. As far as I know, the BIOS of the 7970 does not limit itself when temps reach max (as the new 290's do) so I cannot explain the drops you experienced.

The only PCIe bus that is available on my board (due to the 2,5 slot graphics card) is only 8 lanes, and as far as I know, both cards will then use 8 lanes instead of 16. Is this performance drop calculated in the 180% performance win with Crossfire?
Edited by dXsL - 1/14/14 at 6:27am
post #5 of 8
Quote:
Originally Posted by dXsL View Post

tnx for the answers!

it is actually the "Top" version I have (ASUS HD7970-DC2T-3GD5).
Mine is stable under gaming conditions at 1100/1500 (air) and cpu is a 3550K @ 4.5-4.7 (depending on summer/winter, "liquid" Corsair H100 smile.gif). Temps are around 70C for the gpu and 60C for the cpu.

I have played with both Asus' own program and of course Trixx to overlock the gpu; memory temps are a problem and more speed results in artifacts.

I want constant 120+ fps which currently is only possible with medium settings in BF4, but I would like more quality.
180% performance improvement in Crossfire is more than I could dream of but unstable fps just does not do it for me either. As far as I know, the BIOS of the 7970 does not limit itself when temps reach max (as the new 290's do) so I cannot explain the drops you experienced.

The only PCIe bus that is available on my board (due to the 2,5 slot graphics card) is only 8 lanes, and as far as I know, both cards will then use 8 lanes instead of 16. Is this performance drop calculated in the 180% performance win with Crossfire?

I didn't have FPS drops because of temperature (hottest GPU was ~ 70C), it was some driver issue with CF and BF3 and BF4 multiplayer.

Now I see you have i5 3570K OC'd, don't bother putting anoter HD7970, that i5 will bottleneck your GPU's especially in BF4 which is very CPU hungry game.

Runnig both PCIe @ 8x is not a bottleneck compared to 16x, 8x PCIE 3.0 is more than enough.

I have seen Asus HD7970 DC2T crossfire setups, and top GPU was running at almost 90C due very little space in between two cards, so be very careful.

CHEERS..
     
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post #6 of 8
Quote:
Originally Posted by KingT View Post

I didn't have FPS drops because of temperature (hottest GPU was ~ 70C), it was some driver issue with CF and BF3 and BF4 multiplayer.

Now I see you have i5 3570K OC'd, don't bother putting anoter HD7970, that i5 will bottleneck your GPU's especially in BF4 which is very CPU hungry game.

Runnig both PCIe @ 8x is not a bottleneck compared to 16x, 8x PCIE 3.0 is more than enough.

I have seen Asus HD7970 DC2T crossfire setups, and top GPU was running at almost 90C due very little space in between two cards, so be very careful.

CHEERS..

mantle might change that cpu's stress with dual 7900s.

op, this is what King is saying . . .

i7 4.5 HT off in BF3 MP 64 . . .



look at the usage . . .




here was the usage with HT on (flat at 99% with one and around 90% with the other just before i logged off) . . .



pretty close to Hwinfo64 readings . . .


Edited by rdr09 - 1/14/14 at 7:14am
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post #7 of 8
post #8 of 8
Quote:
Originally Posted by PontiacGTX View Post

Here you have
http://techspot.com/review/738-gigabyte-geforce-gtx-780-ti-ghz/

i played C3 using Very High and 4MSAA with a 7970. i can max it out now with a single 290. i don't think there is much difference between 1080 and 1200.
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