My 90c 9800X3D story

mattius1989

mattius1989

mattius1989

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Over the past few weeks, since upgrading to a 5090, I noticed my CPU running quite warm under medium load. I initially put it down to the warmer weather.

It's cooled by a Noctua single fan tower and the case is a 4000D airflow with the stock 1 in, 1 out fan configuration.

I decided to replace the fans with Noctua units and add an additional 150mm to the front. I repurposed stock fans to exhaust at the top of the case with an additional Noctua fan at the rear for exhaust.

Running a few benchmarks, I noticed that it didn't really solve the problem. I tweaked all the fans to consistent 45% with a critical temp set to 85. Again, the cpu just kept climbing when the GPU was fully loaded.

It then dawned on me that the GPU is exhausting directly into the path the cpu draws from (fan facing the front of the case) and was gradually getting heat soaked while the GPU was under full load.

After tweaking fan speeds a bit more, and slightly undervolting the CPU (-20mv), I stumbled upon advice to undervolt the 5090 to reduce it's temp under load.

I followed a basic guide which, if I recall correctly, flatlined at 900mv, 2500mhz.

After some more testing this has basically solved the issue with a couple of percent performance loss on the GPU.

I suspect the true fix would be to water-cool the CPU to remove the GPU exhaust issue from the equation.

Has anyone had a similar issue with a 5090 or similar and a tower fan on the CPU? Would water-cooling be the optimal approach here?
 
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I put in a 9800X3D the other day, on a 360mm Corsair AIO and my idle temps are very very low, now i dont know if thats me luck with the chip or the 9800X3D in general..but a top cooler or a 360mm rad you cant go wrong.
 
Zeebedy said:
I put in a 9800X3D the other day, on a 360mm Corsair AIO and my idle temps are very very low, now i dont know if thats me luck with the chip or the 9800X3D in general..but a top cooler or a 360mm rad you cant go wrong.
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The cooling was fine until a 5090 was added to the mix. I'll likely make the jump to an AIO soon.
 
Only other option I could think is some sort of 3d printed shroud to funnel air either to the cpu or away from the gpu.

I imagine eventually we’ll get more cases designed around separating gpus from the rest of the components internally. Kind of like the Corsair air 5400? The triple chambered one.
 
I have the 5090 and 9950x3d with 12 fans and the cpu ides around 35c and gaming about 45c odd.
ec8b859c-c7d8-439e-a572-f2d3081467cd.jpg
 
Lian li infinity 140mm and 120mm,changed them to phantek d30 now:)
 
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clone said:
I have the 5090 and 9950x3d with 12 fans and the cpu ides around 35c and gaming about 45c odd.
ec8b859c-c7d8-439e-a572-f2d3081467cd.jpg
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Beautiful!
I'm curious why only 2 exhaust fans with 10 intake fans? Obviously it's working just fine .. and extra venting is flowing about 2x fans' air out of case. That's still a 2:8 imbalance of airflow.
I try to balance numbers so there is just slightly more intake airflow than exhaust (but that's w/ filters on intakes so only clean air enters case).
My guess is changing top to exhaust will slightly lower temps. Could unplug them and see what it does. If temps stay close to same, changing them to exhaust would likely give lower temps / less noise.
 
There's actually been instances of people having ram instability due to how the 5090 vents, it's rare but it does happen. It's usually solved in the manner you've went, which is undervolting. There's no real performance downside so assuming everything is sorted I'd not be concerned about an AiO personally.
 
Gray2233 said:
There's actually been instances of people having ram instability due to how the 5090 vents, it's rare but it does happen. It's usually solved in the manner you've went, which is undervolting. There's no real performance downside so assuming everything is sorted I'd not be concerned about an AiO personally.
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Wait what lol?
Is this a heat issue? As in the 5090 blows hot air towards your ram and then causes it to have a thermal issue?
Jesus! :cry:
 
deviation said:
Wait what lol?
Is this a heat issue? As in the 5090 blows hot air towards your ram and then causes it to have a thermal issue?
Jesus! :cry:
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I mean, a 575W TDP GPU venting hot air out of its arse all over your RAM and CPU can cause problems, who would have thought? The fact a bunch of tech reviewers gushed over the HSF design still puzzles me given the blatant design flaw.
 
What Gray 2233 said. Old GPU were bad enough, but instead of improving GPU airflow to work with case airflow they put holes in GPU PCB so they dump heated air not just front,back toward case side and mobo on component side of GPU, but now dump heated air toward RAM and CPU.
 
doyll said:
What Gray 2233 said. Old GPU were bad enough, but instead of improving GPU airflow to work with case airflow they put holes in GPU PCB so they dump heated air not just front,back toward case side and mobo on component side of GPU, but now dump heated air toward RAM and CPU.
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It's such a poor way of doing things tbh, you want to vent hot air externally as much as possible or at least redirect it from critical areas, but it does the polar opposite.

With the FE it's actually worse, they've a fan pushing that hot air at your VRM/RAM/CPU areas.
 
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