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Message boards : Graphics cards (GPUs) : Two or more GPU's in one system

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TJ
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Message 36938 - Posted: 28 May 2014 | 19:07:20 UTC

Hello, I started a new thread as I noticed something. Perhaps already elaborated in another thread.

I had a PC with a GTX780Ti in slot one (closed to CPU) and a GTX770 (double fans) in the seconds slot, with one slot in between. The 780Ti went hot (limited by Precision X to 73°C), and did not boost, down clocked a bit even to obey temperature target. But the 770 ran steady at 68°C and boosted.

Today I replaced my two 660's for a new 780Ti (EVGA, OC and ACX (double fans)) and put this one in the seconds slot. I placed the 770 from the other PC to the first slot. Now the 770 is down clocked as I set its temperature limit to 72°C, and it went quickly to that value.

So I get the conclusion that the first card will be the hottest, perhaps it is best to place a "light" card in the first slot, that will not become to hot and stays at base clock or even a little boost, and put the "heavy" ones in the second slot (and third if available/room).

I'm interested to read some thought about this.
As always thanks for your time.

NB: a second thing I noticed is that a PC with two GPU's who both have two fans (axial ones I belief), make a lot of noise, almost to much. I will experiment with this in the coming days.


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localizer
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Message 36939 - Posted: 28 May 2014 | 19:15:13 UTC - in response to Message 36938.

Hi TJ,

I'm not a fan of the non-Titan cooler on these cards - I have found the best way is for the hot-air to be exhausted out of the case, rather than stirred around inside with all the other components.

I am about to build a 780Ti & 770 host - both Titan coolers - I have found this cooler to be quieter and kinder to the other components in my case.

I guess it comes down to individual preferences, but I am trying to build smaller these days and the ACX coolers don't work for me.....

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Message 36951 - Posted: 29 May 2014 | 11:34:49 UTC
Last modified: 29 May 2014 | 11:35:24 UTC

Do you guys leave the sides off of your cases or run them with them on? I run all of my machines with the sides off and they seem to run cooler. I reuse older cases alot though, so that may have something to do with it too.

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Message 36953 - Posted: 29 May 2014 | 16:39:22 UTC - in response to Message 36939.
Last modified: 29 May 2014 | 17:19:26 UTC

I am about to build a 780Ti & 770 host - both Titan coolers

Do you mount the titan coolers separately and where du you get it from? Or buy a card WITH titan coolers? I've the same problem with my 770 (MSI Twin Frozr). The Card runs hot (78°) so I have to throttle it for running with 70°. Like you told the problem is, that the cooler is swirling the air within the housing. Opening the side-panel brings it down 5-7°.
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Vagelis Giannadakis
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Message 36955 - Posted: 29 May 2014 | 20:04:24 UTC

TJ you are right in your observation about the card in the first slot getting hot. I observed this with my setup too, although a much humbler one with a 650Ti and a 750Ti. The best-cooled card (that is, the one with the most efficient cooler and the smaller tendency to get hot) should be placed in the first / upper slot.
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Message 36956 - Posted: 29 May 2014 | 23:49:32 UTC

What Localizer is referring to is the reference cooler that was originally, and still, available on the Titan cards and is now offered on most of Nvidia's cards. The reference cooler has a blower style fan that sucks air from inside the case and exhausts it out the back. I prefer this style myself though they can be noisier depending on the case your system is built in.

The coolers like EVGA's ACX cooler with the fans that look like your typical case fan do not exhaust the heat out of the case. They just dump it into the case for other video cards and your CPU cooler to suck in. If you do not have a case with several exhaust fans, like a Corsair 600T, your going to have heat issues. I like the 600T and similar cases because they have a grill in the top of the case and a fan to push heat right out the top.

TJ
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Message 36960 - Posted: 30 May 2014 | 7:34:25 UTC - in response to Message 36955.

TJ you are right in your observation about the card in the first slot getting hot. I observed this with my setup too, although a much humbler one with a 650Ti and a 750Ti. The best-cooled card (that is, the one with the most efficient cooler and the smaller tendency to get hot) should be placed in the first / upper slot.

Thanks for the conformation Vagelis, that was where I was looking for.
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Message 36961 - Posted: 30 May 2014 | 13:23:07 UTC

I see the same thing here. On both my dual 780Ti and dual 680 machine the top card gets warmer. On the 780Ti machine it's only a few degrees. On the 680 machine it can sometimes be close to ten degrees. I'm looking at some ways to improve that now. It has a lot to do with your case set up. The 680s used to be in the case the 780Tis are in now and there was not as big of a temp difference as I'm seeing now with them in an older case of mine (Antec 1200 vs Antec 900).

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Message 36963 - Posted: 30 May 2014 | 14:26:30 UTC - in response to Message 36961.

Yes indeed, 2 degrees difference in the dual 780Ti set up and I had 10-12 degrees difference in the two 660 set up. That last one has its mall stock cooler CPU-fan and a side fan among others. Replacing the second one with a 780Ti, made the 660 quickly to over 80°C. So I had to lower the voltage and the power target to get it lower. It runs at 77°C with fan at max (is 74% for those cards), but also CPU is now at 64°C (4 Rosetta's) while it was always around 56°C.

I will remove the 660 later today and see what happens then.
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Message 37762 - Posted: 30 Aug 2014 | 17:35:55 UTC
Last modified: 30 Aug 2014 | 17:59:20 UTC

In my signature is a link to my computer's listing and a picture of its insides over at Overclock.net.

The case I use is a somewhat dated and cramped Antec Nine Hundred, but considering that, it does a great job maintaining a relatively cool internal computer temperature with its current setup, even with the side panel on.

It has a built-in 200mm top exhaust fan for starters. I put two newer 120mm 4-pin PWM fans in the lower front of the case for air intake and removed the clear plastic fan mounting on the side panel so that the metal mesh/grill in this area (roughly a square foot's worth) is open for airflow to come in on the side toward internal components.

My CPU cooler is a Corsair H80i liquid cooler. On its radiator a have two more 120mm 4-pin PWM fans, and though this goes somewhat against the general current wisdom on the mater, I have this radiator on the upper back of the case blowing air out. The negative effects of this layout are largely mitigated by the fact that my two SLIed EVGA Titan Black Superclocked cards with their stock Titan-style coolers pull air in across their heatsinks and blow it out the back of the case so that they don't heat up the other components in the case (such as the CPU radiator) nor each other.

An additional advantage for this kind of setup is that cooler air has a well defined and efficient path to follow into the case, across the internal components and then out again on the opposite ends once it has warmed up where it is less likely to cycle back in again. This way airflow is not having to fight against itself, nor convection and the tendency for hotter air to rise, but instead uses that to its advantage.

This setup helps to maximize airflow through the case and the overall effectiveness of its cooling potential, keeping my GPUs and CPU more than adequately cool for my needs. Though as you may imagine, dust buildup is also somewhat more of an issue because of it, so I have to stay on top of its maintenance that much more.

But yes, overall and in general I agree with the others that exhausting hot air from the case is much better than having it just mixed around inside. That is certainly so with my setup.
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