Corsair H150i RGB Pro XT

[marcusob]

I have the following

ASUS Crosshair x670e Hero

AMD 7950x

Corsair H150i RGB Pro XT

I am running some benchmarking CPU work - to keep everyone of the 32 threads (16 cores) at 100% load.

For this AIO with my setup, when my CPU package temperature gets to 95 degress it continues to operate at the same clock speed but the voltage drops from 1.5 to 1.15, so this might be throttling (not sure). The AIO has the pump and fans set to Extreme in iCUE, and the Coolant Temperature always hovers around 32-33 degrees.

The CPU package temperature never seems to drop below 95 degrees, and the Coolant Temperature doesn't go up or down. So is my AIO actually cooling the CPU or not ? I dont see anything getting cooler, and the CPU doesnt seem to be doing anything different apart from the Voltage being lower, which may be throttling.

What is supposed to happen whe nruning 100% load on my CPU, is the AIO supposed to cool down   the package temperature or not ?

[c-attack]

The cpu gets hot because you apply voltage to the underside. That heat passes through the cpu and is then conducted through the cold plate on the AIO and into the liquid stream. Then it’s transported to the radiator and released. The AIO is waste heat management. It’s keeps the cpu from continuing to increase temperature during use, but it can’t stop it from getting hot in the first place. If you hit 95C one second into a load, that’s a cpu and voltage issue. An AIO limitation looks like — it starts at 80C but then slowly creeps up and up to 95C as the load continues. 
 

Im not a 7950X owner so I can provide and tips for tweaking the voltage or explaining its behavior. However, the reviews are all pretty clear on the expected temps. 
 

“The 7950X regularly hit 95C during the test run, which AMD assures us is expected behavior - the chip is designed to consume all available thermal headroom to provide faster performance. The 95C thermal threshold is within safe operating limits, so it won’t result in degradation. “

[LeDoyen]

Basically, wether you have a small air cooler or a big AIO, you'll (almost) always hit 95°C under heavy load, but the AIO will allow the CPU to hit higher frequencies, when the air cooler will have to limit way sooner.

Same temperatures, but better performance with a better cooler.

[marcusob]

Ok got it. Thanks a lot for the info.

I think in order to see if the AIO is making much difference I can set it teh AIO to Quiet mode in ICUE and see how long a 100% CPU job takes to complete. Then change the AIO to Extreme mode and do the same test. Theoretically the Extreme AIO setting will cool the CPU better, and help prevent/reduce throttling, thus the high load CPU job will complete faster. I want to see if the settings on the AIO actually do make performance of the CPU better or not. I want to see if the AIO behaviour is dynamic and affetced by the fan settings - if not I will leeave it on quiet mode.

[LeDoyen]

if you reduce the fan speed too much, and the water gets too hot (i believe it's 50-55°C?) the controller will take over and blast the fans to full speed to avoid overheating. If you hear the fans take off, you'll know what it is 🙂

But i'm not sure you'll see much difference between the cooling presets. often quiet/balanced/extreme don't match well with the ambient temperature you have and your CPU heat output.. they are very generic presets and tend to run the fans too fast sometimes.

If Quiet is too fast, you could make a new fan curve preset, controlled by the H150i temperature (water) and run the fans slower.  Remember all watercoolers (AIO or custom) have a 60°C hard limit, so you'll want to max your fan speed just before that temperature. You can make a couple of fan curves, one quiet, one louder for maximum cooling (unless the extreme profile does just that) and compare.

The difference may be tiny, so you'll be better off watching what maximum frequency the CPU gets to. The time to complete a task may not change significantly, but who knows..

 

Just to illustrate, my current work laptop came from the factory with what i'd qualify as a thick layer of plaster of paris instead of thermal paste. the thing was loud AF, and the CPU constantly hitting 95° and throttling. That's kind of normal it's a beefy I7 for CAD work.

I took the thing apart, cleaned the CPU/GPU and applied some Kryonaut on it. Now it still thermal throttles at 95°C, but 400Mhz higher than before on all cores, and is way quieter under light load and idle.

That's the kind of behaviour manufacturers are leaning towards with the current generations of CPU. Maximizing performance with the thermal headroom your cooler has.

[c-attack]

You probably won’t see completion performance differences unless you hit the throttle point or some other temperature imposed frequency behavior action. However, there is an easier way to asses AIO performance in relation to cpu temp. +1C to coolant temp = +1C to cpu temp. Same thing on cooling with -1 to -1.  Back to back runs can create differences with residual heat in components or the case, but you can shift between fan speeds and pump speeds mid job to assess impact. 
 

At moderate or better fan speeds you won’t see much difference in small 100-200 rpm fan speed changes. There’s nothing overly magical about the pre-programmed curves and like any preset its suitability is highly dependent on the initial baseline temperature. The curves have been tweaked over the years, but the primary aim is a “typical user” and it tries to be as quiet as possible for as long as possible, before rushing toward maximum at a predefined point. There’s nothing special about 40C liquid temp. It’s 1C different from 39 or 41C. Nothing else, but they had to pick some temp. It is where most CPUs in standard configuration will get into the 90s on a sustained load. If you are running long cpu renders, encoding, or whatever, you may be better served by setting the fans to a fixed speed at the highest setting you are willing to tolerate. That is highest possible cooling vs noise level from the very beginning and has a better chance to keep the coolant level lower. 
 

Pump speed is a bit different. Most users will see zero difference between the three tightly grouped presets. However, cpu die size does matter and larger chips may see some benefit from higher speeds. With a free hand or in custom loops pump speed has more consequence, but typically pretty minimal with most AIO units. 

Edited May 27 by c-attack