[SOLVED] How should an AIO fan curve be? And what is the CPU OPT?

[libykim]

Ryzen 3700x on Gigabyte Aorus SIV auto (Smart Fan) Setting revs up and down more than I'd like it to.

Is it best to keep it that way on auto, or should I change it to a custom curve?
If so, do I just change the CPU, or do I change both the CPU and the CPU OPT?
And how should the curve be?

 

[CountMike]

Ryzen 3700x on Gigabyte Aorus SIV auto (Smart Fan) Setting revs up and down more than I'd like it to.

Is it best to keep it that way on auto, or should I change it to a custom curve?
If so, do I just change the CPU, or do I change both the CPU and the CPU OPT?
And how should the curve be?

Which AIO ? On mine I set fans 50% up to 50c and 100% at 65c. That way speed oscillations are at minimum because coolant is at low temps when CPU heats up. 62 to 65c is best for PBO to go highest for best performance.
CPU_OPT is just for another eventual cooler fan so both fans are synchronized.

 

[MadsModsat]

As mentioned above, it depends on what AiO you have, CPU as well.

I had an NZXT Kraken x62 280mm AiO and I had the fans at 35% until 55'c. From 55'c it was increased to 45%, at 65'c it was set to 50%, and from 75'c and beyond, it was set to 65%

The pump was on a factory "Silent" preset, so it was at 2000rpm when under light load, and 2700rpm during gaming and stresstests

This was with an i9 9900K (stock settings), and temps never went above 70'c with this setup. The noise from the AiOs bothers me when they are running at high RPM.

I performed a lot of different temperature and load tests, and I quickly noticed, that at a certian point, increasing the radiator fan RPM had little impact on cooling performance, but became very loud instead. So I spent a lot of time figuring out minimum fan RPM for efficient cooling.

So the fan curve I used wasn't a smooth gradual curve, instead I had it configured to everyday tasks like browsing and watching video never resulted in a temperature where the fan RPM would increase or decrease.
It was more like a step ladder curve, where gaming was within a certain range, minimal load was in a different range.
That way I avoided the annoying sound of fans increasing or decreasing often, when watching a video for example. Most tasks performed on my PC, had their own step in the fan curve, you could say.

I've since then ditched the AiO and returned to air cooling instead.

 

[Karadjgne]

You are dealing with a Ryzen, not Intel cpu. There's a significant difference. With Intel in low power states like idle, bios drops voltages and clocks across all the cores, but all the cores retain some activity with background tasks. So you'll get small bounces across one or two cores periodically. With Ryzen in low power states, it shuts down all the cores, parks them, so any and all background tasks happen to just 1 core. This puts single core use as much higher than Intel which has spread core use over all the cores.

As a result, idle temps for Ryzen are considerably higher than what people have been expecting from Intels for years. It's a new standard.

This has a side affect of upsetting fan curves, most settings the fan doesn't move much (if any) below @ 40°C, but with the Ryzen right around that break, it gets really touchy as temps can bounce from @ 40°C to 70°C and back in 3 second bursts.

The best way to combat that is if the aio has software capable, use liquid temps not cpu temps for cooling basis as liquid temps are totally stable and take far longer to change even 1°C. Zero bounce. Nzxt cam I had set for a low curve between 30°C and 40°C, and if liquid temps are exceeding 40°C you have larger issues than cpu fan bounce.

Barring that, you'll need to lower the curve radius, instead of a sharp incline in duty cycle, flatten it out. That means fans will spin a little faster at low power states and a little slower at higher loads.

 

[libykim]

The best way to combat that is if the aio has software capable, use liquid temps not cpu temps for cooling basis as liquid temps are totally stable and take far longer to change even 1°C. Zero bounce. Nzxt cam I had set for a low curve between 30°C and 40°C, and if liquid temps are exceeding 40°C you have larger issues than cpu fan bounce.

Barring that, you'll need to lower the curve radius, instead of a sharp incline in duty cycle, flatten it out. That means fans will spin a little faster at low power states and a little slower at higher loads.

First off, thank you both for the detailed answers.
I am getting a general picture of how the fan curve should look like now.
I have a Deepcool Castle 240 v2 and I don't think this one has a software capable. So I'll have to do some tweaking on my own I guess. Anyway, thank you guys again.