Question d4000 airflow 6900xt toxic (360mm radiator) airflow help required.

May 2, 2020
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Hi everyone,

I was planning to build a pc, but with the shortages, I just bought what I got and that was bigger than initially planned... I was planning to have a „normal“ 6800xt but got a 6900xt toxic at msrp. Still more expansive but it was at msrp so I bought it... I already switched from a 750 to 850w psu. But now i struggle to build proper airflow in a d4000 airflow...

current config:
cpu: 5900x pbo on (86 c max at cb23)
cpu cooler: nh-d15
mb: asus x570-i
memory: 2x16gb 3600 cl18
gpu: sapphire 6900xt toxic (radiator front push intake)
case: 4000d (one intake fan on top and one outtake at the back)
psu: hx850i

One issue is that gpu fan are some time not spinning when cpu has stress as I do use the machine for some rendering(cpu only) work. I don‘t found a way to control the gpu fans...

any suggestions are welcome.

Regards David
 
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COLGeek

Cybernaut
Moderator
Front, side, and bottom fans are generally intake fans. Top and rear are exhaust.

I see what you are trying to do with your top fan, but it may be working against you (hot air rises).

Do you have any bottom fans? Also, hard to tell from the picture, but is there room for a top fan (as exhaust) near the CPU cooler (above it)?
 
May 2, 2020
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Front, side, and bottom fans are generally intake fans. Top and rear are exhaust.

I see what you are trying to do with your top fan, but it may be working against you (hot air rises).

Do you have any bottom fans? Also, hard to tell from the picture, but is there room for a top fan (as exhaust) near the CPU cooler (above it)?
the issue i have is, that the gpu radiator is 360 and takes all the front. i configured it so that they push air through the radiator into the case but the fans do only spin in relation to the gpu usage. so when i do rendering only the cpu is working... so low or now intake through the front. i installed the top fan to push some air in in this case as they isn‘t any other. i actually aim to positive pressure system to prevent dusting. I just don‘t see how to archive it...
 

COLGeek

Cybernaut
Moderator
the issue i have is, that the gpu radiator is 360 and takes all the front. i configured it so that they push air through the radiator into the case but the fans do only spin in relation to the gpu usage. so when i do rendering only the cpu is working... so low or now intake through the front. i installed the top fan to push some air in in this case as they isn‘t any other. i actually aim to positive pressure system to prevent dusting. I just don‘t see how to archive it...
You could put case fans on the backside of the rad, attached to a fan controller, or motherboard headers foe additional airflow.
 
May 2, 2020
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You could put case fans on the backside of the rad, attached to a fan controller, or motherboard headers foe additional airflow.
As they would not be controlled by the same source, would it not make problems when the fan on the push side does spin different than the pull site? assume the gpu spinn full speed(push) and case fan(pull) do spin low speed. Also would i add two or one fan at the top to oull air out?
 

Phaaze88

Titan
Ambassador
Hello, @Mopf !
As someone who has done hybrid cooled gpu + air cooled cpu, but:
-with all Noctua fans: A15, A14, F12, S12A, IPPC 3000 A14 & F12
-D15S(dual A15) instead of the regular one
-1080Ti(Kraken G12 hybrid kit + Celsius S36) instead of 6900XT
-H500P Mesh instead of 4000D Airflow(the airways between these 2 models isn't going to be all that different)

Remove the top fan, and you're done. The D15 already draws air from up there on its own, and the front is a given thanks to the rad fans. The top fan is just creating turbulence.
Now you have a perfect front to back airflow.
Consider removing that rear fan too, with the exception that you run it faster than the D15's fans. You have to - the alternative being that it's more effective to leave it empty; the D15's fans do more than just move air through the heatsink.
Perhaps also consider moving the rad fans to pull instead of push. Less air blowback at the radiator - slightly more efficient than push.

If you want to get thermals down further, then consider:
-running fans faster within what you are able to tolerate.
-undervolting both cpu and gpu. By default, both overvolt to guarantee their clock speeds. Even a negative offset on the cpu of 0.01v would help and not harm performance. I'm not familiar with the Radeon Software though.

There's too many open gaps in the chassis for the whole positive/neutral/negative pressure argument to apply. Ironically, it matters more in an airflow restricted model.
Dust: It is inevitable. Organize a cleaning schedule.
Ironically(again), an airflow restricted model can see a little less.


From the testing I did in my own chassis, I feel that top exhaust fans don't do that much cause the whole cpu air cooler + front intake hybrid gpu follows a different 'flow' from the usual air cooled gpu setups.
With most air cooled gpus, they're dumping their heat in the chassis, and you want more exhaust fans to deal with that.

While the front intake hybrid does the same thing, the air coming off the radiator is going to be COOLER than what typically comes out of an air cooled model. Top exhaust won't do much for this; your components behind the rad will still appreciate the air coming from there.
It'd be better to have the air pass straight front to back here - forget top exhaust.
 

COLGeek

Cybernaut
Moderator
As they would not be controlled by the same source, would it not make problems when the fan on the push side does spin different than the pull site? assume the gpu spinn full speed(push) and case fan(pull) do spin low speed. Also would i add two or one fan at the top to oull air out?
Not really. Just a nice cool GPU is the only by-product of doing so.
 
May 2, 2020
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I could not install a fan(at least not the once i have, a slim version may fit) above the cpu to exhaust. So I run r23 (10min) two times on the following setup:

as mentioned above, one intake top and one exhaust at the back:
max. 86c
21750 pt(second run)

second setup, one additional pull on front radiator and one exhaust at the back:
max. 86c
21780 pt(second run)

What i noticed during the run, the cpu start with all core 4,425ghz and then quickly go to 4,4ghz and than to 4,375ghz on all core. So I assume it throttles down when reaching 85c.

Also after a while the front fans(gpu radiator) start to turn as the gpu is getting passive warmed (lol) but I run another test with nearly identical results.

I went to the bios and set pbo to negative 10 with 200mhz that reduced temp to 70c but that cost me 1000-1500pt all core goes to 4,25ghz. So I think the CPU fan might just be the limiting factor here...

For now I set max temp to 80c, feel more relaxed that way. Strangely enough cb23 performance increased to 21900 pt...

Considering getting 280aio for top exhaust what do you think?

FYI the d4000 top mesh does not catch dust... I noticed this when I moved the top intake fan as there where dust below the mesh...
 
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Phaaze88

Titan
Ambassador
Considering getting 280aio for top exhaust what do you think?
I currently have a dual hybrid cooling setup going right now, and I don't care for it. It's a pain in the butt.
Lots of screws involved, and cleaning is tedious, especially when removing and reinstalling both coolers - and I actually enjoy the cleaning part to some extent.

Next PC cleaning I get around to doing - which I haven't been doing as often, go figure - I'm taking the cpu hybrid cooler out and putting the D15S back on it. I just hope it's compatible with the direct die mount, or I'm boned...

Air cool one, hybrid cool the other. If I'm going to liquid cool both, I may as well go the custom liquid route - but I'm not interested in doing that, so air + hybrid it is.
As for which one to keep the hybrid cooler on, that was an easy decision to make after having tried both.
Gpu wins, but the biggest downside is that it isn't as conventional as cpu hybrid.

I say, don't do it.
[The above is all opinion based on personal experience.]


FYI the d4000 top mesh does not catch dust... I noticed this when I moved the top intake fan as there where dust below the mesh...
Oh, it works, but not for what you think. It's there for reducing dust when your PC is off.
 

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