PC swapped 2xTitansB for 3x780Ti & tweaking

[rappet]

Hi Guys,

for those who are interested in AC system and Benchmark with finetuning GPU.
I did not want to post this in the Bencmark thread, because it is more about the finetuning.
I played with the GPU settings before, just to learn a bit, but now I had to play with the settings to get the system work, because the temps were getting to high.

To start with I would like to ask you pro guys this:
What can I do with the 'GPU CLOCK OFFSET' and 'MEM CLOCK OFFSET'?
Now I just tweaked the 'Power target' and linked 'temp target'

I looked up the old Benchmark with OR (release 1.20) to compare.
This sytem had one gtx275 for the monitor and 2 Titans Black to render.
The result was:
2x Titans Black: 15.03 Ms/sec
2x Titans + gtx275: 15.79 Ms/sec (turned monitorcard on as well)

The machine with 2 Titans are swapped for 3x 780Ti.
with temp targets on 82 degrees
This is the result;

1x 780Ti n01: 8.23 Ms/sec, 81-(41)-(30) degrees
1x 780Ti n02: 8.12 Ms/sec, (38)-83-(30) degrees
1x 780Ti n03: 8.15 Ms/sec, (43)-(38)-75 degrees

3x 780Ti:
(fanspeed 100% and temps were still rising)
then I noticed that PC on the backside had only about 20cm space for airflow! oops.
I hope there is a auto killswitch to protect the GPu from overheating? must be.. but probably a little higher then 90 degrees?
Anyway...I killed the test, rotated my PC a little that the space behind the PC was becoming a meter.
Now the result is
3x 780Ti: 22.29 Ms/sec, 92-96-76 degrees
I noticed the second gpu clock was dropping and rising very quickly.. I guess that is the auto killswitch beause of too high temps
I probably have to conlcude that the PC is not having enough aircooling to run 3 780's

So, I added a fan (I use in summer to survive in my workspace with GPU rendering and sun shining outside
I directed the 40cm diameter fan on the side and back of PC and starrt rendering again to see what happens this time:
the second GPu is getting the hottest and after a while it is also hitting the 96 degrees

So, now I kicked out the fan again (I'll keep it just to cool myself in summer
and I played with the power targets the GPU and I got this result after finetuning
3x 780Ti: 20.40 Ms/sec, 83-88-70 degrees
n01: 57% (849-692mhz, 83 degrees, manual set fanspeed 100%)
n02: 57% (849-692mhz, 88 degrees, manual set fanspeed 100%)
n03: 100% (1124mhz, 70 degrees, auto fanspeed 75%)

I have to say that the renderspeed drop down (by setting power target from 100% to 57% on two GPU's)
is not that big as I would expect: from 22.29 to 20.40 Ms/sec.
but adding the GPU seperately means a dropdown of almost 18% (8.23+8.12+8.15=24.50, to 20.40 Ms/sec)
and that is because not having an optimal aircooling.
(I had to remove one fan (bottom) because the new power unit was larger
Maybe I will try and install the removed fan on the front side.

I got another question:
How can I check to be sure which GPU is the one I use for my monitor?
The confusing thing is that in Octane Render the GPU 1,2 and 3 are the reversed shown in the EVGA Precision X (I use for tweaking).
In the photo you can see the three GPU's and the top one I am using for my monitor.
The bottom one is near the Power unit, but my guess is that that is the one with the lowest temps, because the right fan on the GPU has the most space to breath.
Am I correct?

Greetz,

[glimpse]

I'll leave OC questions for others who know more =)
as for temps jop, the lowest temp should be on the bottom GPU, just because it has most airflow =)

what I would do, probably try to put as much airflow as possible..turning all fans (except on the back) to take air in..this should force a lot of fresh air from outside creating pressure to move anything that is already in the case out..

Ideally You should tie You cables nicely & have at least a good fan from right (front of the case) to provide as much air as possible..that should help to keep Your temps low.

these 780Ti are power hungry & pretty hot..

[smicha]

Rappet,

Use MSI afterburner - the numbering of gpus is exactly done in the same order as on your motherboard - the closest gpu to cpu is #1 and so on. And this should be hottest one on air (it absorbs heat from gpu #2). Look at the screenshot - I use msi monitoring at my task-bar - the first yellow row is #1,... (at idle and at load while rendering).

This is what I wrote earlier - an air-cooled system with 4 slots taken by gpus does not allow to use their full power. Once the temp limit is reached (i.e., 80C, you can set it in MSI afterburner) your cards will automatically reduce their core clock to preserve lower temps. And you can do nothing about it on air (or use raisers to separate them, but we are not talking about such coin-mining solutions).

Your cards - as you wrote - go at even 692 mhz. But on water they can easily hit 1200mhz at stock volts (1.2V I hope). So you see you loose almost 45% of their power on air. And temps are 80-95C, while on water 40-45C at low rpm fans, generating very little noise.

So install MSI afterburner and look at graphs depicting power, temps, core clock, memory clock, voltage and you see how your hottest gpus slow down while rendering.

You can do a test - take out of your case the middle card and leave only two that are two-slot distant from each other. You should see temp improvement.


PS. If you are not sure which gpu is which, set manually (afterburner) a fan speed at 100% and try to listen which card generates noise.

[Jonas]

Definitely looks llike a case for watercooling or you could submerge it in mineral oil.

Another variant you could investigate, is one of these cases that rotate the motherboard 90 degrees, so you get 3 case fans on the very bottom of the case blowing upwards onto the cards above, creating a stream of cold air between them, but like i said, i am not entirely sure how viable it is, so you have to check it out, plus there always will be some noise.

[mark0spasic]

Hi, maybe you could look at this forum :http://forums.evga.com/tm.aspx?high=&m= ... =1#1976578
there is interesting solution for placement of cooler

[glimpse]

markOspasic - that's an interesting idea for those who don't have case with fan mount in front (that in my eyes is pretty much the must while building multi GPU rig) or maybe, the fan is blocked by drive cage. Haven't seen this, but it seems that's an option in some cases - thanks for sharing! (just keep in mind that it will work only with reference coolers, as non reference operate differently =)

[rappet]

Hi guys,
Thanx for your feedback.
I came up with the idea of tranSfering the complete system into another case (<€200) with good specs for aircooling
and I ended up with the Corsair Graphite 780T
http://www.overclock3d.net/reviews/case ... t_review/1
Cheers,

[glimpse]

Rappet, nice choice! if You like the way it looks =) it does provide plenty of airflow =)
here's one more video on that: https://www.youtube.com/watch?v=IihNgyt-ztE
(just love the way Dimitri put a showcase for those review without BS =)

[rappet]

Rappet, nice choice! if You like the way it looks =) it does provide plenty of airflow =)
here's one more video on that: https://www.youtube.com/watch?v=IihNgyt-ztE
(just love the way Dimitri put a showcase for those review without BS =)

Hi Glimpse,
yes I did see that review and liked it too.
Linus also has a lot of reviews, but you probably know
\http://www.youtube.com/watch?v=JIyPeXUfFKE
I do not know yet if I like the way this case looks... function is my first priority.
All hardware and furniture in my workingspace is black and white with a touch of red.
Yellow case would be like cursing
I'll probably go for the black.
I do not mind the plastic.. Darth Vader did not \
He went for function too I bet
cheers,
offtopic now:
Funny to see these 'serious' reviews on the helmet and not putting on the helmet or having the helmet on not to be recognized?
I'll bet some guys use them for other things then Haloween
http://www.youtube.com/watch?v=d2bmn3104bY
http://www.youtube.com/watch?v=mGbECYbYoIY
http://www.youtube.com/watch?v=KyiOwOtL-vc

[rappet]

Hi guys,
Thanx for your feedback.
I came up with the idea of tranSfering the complete system into another case (<€200) with good specs for aircooling
and I ended up with the Corsair Graphite 780T
http://www.overclock3d.net/reviews/case ... t_review/1
Cheers,

I did transfer end ended up with a 3x780ti that was getting to high temps, even within this new case Corsair Graphite 780T.
Because of the larger-then-normal PSU I only have one fan on the bottom, but that should not be the reason.
I suspect the MSI Twin Frozer Gaming GTX 780Ti is not that suitable for 3SLI without having slot space between the cards?
I have another case with 4x580 withous slot space and they work fine with the temps.
To check if it the card design difference I might swap 3x580 to the 780T case to see if the cooling of the case itself is OK.
For now I have removed the middle 780Ti card and ofcourse the temps are super low now.
I'll get back later with photo (case looks awsome outisde and inside!!!) and/or I might post a review on Glimpse' thread about cases
Cheers,