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Understanding the H100i v2 temperatures readings.


Aldem

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So my ambient temp is 27.9 C (Summer... :/)

 

On the quiet mode:

 

Idle temps

34c-35c

Fans: 1380-1440 RPM

Pump: 1860-1890-1920 RPM

 

 

On the performance mode:

 

Idle temps

34c-35c also

Fans: 2100-2160 RPM

Pump: 2790-2820-2850 RPM

 

 

I may not understand liquid cooling well, but shouldn't my temps be lower when in perf. mode ? Or is it because the liquid is at my ambient temp ??

 

However, when doing a blend test in Prime95, my readings for the CPU are 57c-60c, no matter if the H100i is in quiet or performance mode.

 

The temperatures ARE fine, although I don't understand them.

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The missing item from your list is H100i Temperature (water temperature). It is found in the last panel in the Link home display. It is the essential medium that connects all the other factors. I am a little pressed for time, so I am going to recycle a prior post along the same lines.

 

The fans' job is to aid in the removal of heat from the water. They do not cool the CPU directly. The actual heat transfer from the CPU is through the cold plate and TIM material. This is not something you can regulate and the transfer rate is more or less fixed. The water in the system is the 'holding tank' for that transferred heat. As you add heat into the water, it's temperature will rise. Whatever your water temperature, this becomes the effective base line (minimum possible) CPU core temperatures. This is the variable you can control, however the range of your water temperature is somewhat small. So, if you have a 30C starting water temperature (your core temps will also hover around 30C) and then you initiate a stress test that brings the water temperature to 38C, the most you could ever possibly reduce the CPU temperature with any fan speed is 8C, by bringing the water temperature back to where you started. Now 8C sounds like a nice drop, but in reality nothing is 100% efficient and you can't get back down that far until the load stops. Maybe 5C at 2000 rpm. Maybe 4C at 1500 RPM. And now there is the issue. Do I want to double my fan noise to take 1-2C off my CPU core temperatures? Probably not.

 

You cannot prevent voltage from passing through the CPU. The cooling is done after the fact on the other side. It prevents heat from being retained in the CPU. So if you set your Vcore to 1.80v, it won't matter how fast the cooler transfers the heat out, you are melting the silicon the instant the voltage touches the CPU and that will always happen first. You cannot stop the instant temperature rise in the CPU material when you apply any voltage. You can only transfer it out after the fact. This is how all coolers work, air or water. Exotic cooling methods involve lowering the base temperature of the CPU to something so low that even the +150C you are adding will still keep the CPU below it's melting point.

 

Pump speed usually does not have much effect on all in one closed loop coolers. The total system length is short and each unit of water can make the trip from cold to radiator and back in a very short amount of time. A faster pump speed would allow more heat to be brought to the radiator, but this will only improve your temperatures if that is the limitation and not something else like heat transfer rates on the die, fan speed, etc. I haven't seen anyone yet report meaningful differences for casual use. A high load, extended duration scenario might show some advantage. Either way, it will never make a difference at idle.

 

I am waiting for you to come back and tell me your H100i temp is 33-34C (when the room is also 28C). That is a fairly normal delta for water temp above room temp. CPU waste heat contributes in only a minor way while at that stepped down CPU frequency, assuming you have C-states, EIST enabled. Most of that water temp is the result of total system waste heat. You can read that as your internal case temperature is also 33C when you took those measurements. You can often compare your water temp to other hardware temps like your motherboard sensor or idle non C: drives. Your case design and airflow are large factors in this. I have an Air 540 case with no drive bays to block airflow and 3x120mm front fans driving air straight through the case. My water temp usually runs about 2-3C above room temp. That is about as good as you can get, but it only gives me a 1-2C core temperature advantage -- nothing to get too excited about.

 

They key item to watch is that water temperature differences between idle and load. That represents the amount you can reduce your CPU temperatures. Most people new to this use too much fan speed. You don't need it until you start getting close to the end of your CPU comfort zone.

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OK, +5.5C above room temperature. Very normal. Motherboard sensor also likely between 29-31C, so that reflects your approximate internal case temperature. I don't want to comment on the package temperature. That is a very CPU model specific value and not always indicative of actual core temperatures. On HW-E, it can run as much as +14C above the highest core temp, as mine is now at idle. I have no idea how standard Haswell reads. In all that I wrote above, read individual core temperature any time I used "CPU temp" or similar.
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I did subsequently see your other post and Link home screen. Idle temps are hovering right around the water temperature. Water temperature is at an expected level above room temperature. I don't see any problems at all, although your load results might be more telling if there was an issue.

 

One thing is for sure, you can relax your fans a little at idle. You don't need 1800 rpm to maintain idle. 1000 rpm would be plenty and perhaps that might raise your water temp by 1C or not at all. Either way, most people not above 50 degrees Latitude need to make specific fan curves for Summer and Winter. The pre-programmed fan curves are based on an approximate 20-23C base temperature. A lot of of us are going to be above that all Summer long. There is nothing significant about 40C water temperature. It is all relative to your starting water temp. If my case temp is 36C and the water temp is 37C, I cannot reduce my water temp below that 36C with the radiator fans. I would need to cool the case. When the whole room is 33-35C, that isn't possible either.

 

Is there something specific you are wondering about?

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Thanks for your tips.

 

I read some people on the internet having 25-30c idle temps, but it all depends on the ambient temps, CPU arch, loads, installed softwares, etc.

 

Guess what I'm wondering is the utility of having quiet, balanced and performance mode if all 3 gives, at least in my case, the same results, even when using Prime95.

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Guess what I'm wondering is the utility of having quiet, balanced and performance mode if all 3 gives, at least in my case, the same results, even when using Prime95.

 

It only means for that test, in those conditions, fan speed is not the limiting factor in your cooling. You could also read that as your H100i is already expelling as much heat as it can. This is another reason you may not need excessive fan speeds. I suspect if you let Prime95 run long enough, the water temperature would climb further and at that point fan speed could reduce it those few degrees. Water temperature is generally slow to change, up and down. You are adding heat to water from the CPU. You are removing it from the water through the radiator fins. If the water temp is not changing, you are removing the heat at the same rate it is added. This is the ideal condition and you cannot take the water temperature below that case ambient level. You can tip the balance the other way by using more voltage, a stronger load, or a CPU with a larger power draw. A 4790K, even when heavily overclocked uses a lot less wattage than an overclocked 6950x. The temperature limitation on a 4790K will also the CPU itself.

 

Quick Summer time tip: use Quiet fan mode all the time. You might have to let it out a little more on some CPU intensive games, but that should cap the fan speed issue. It is at least a starting point for developing your own curve.

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I may not understand liquid cooling well, but shouldn't my temps be lower when in perf. mode ? Or is it because the liquid is at my ambient temp ??

 

The temp of your CPU will depend on your liquid temp (H100i temp in Corsair Link). The fans won't cool your liquid to below ambient temps, so your ambient room temp is going to be a baseline for your water temps.

 

What I do is I set a fan profile based on liquid temps. I let my liquid get to 40°C before I really ramp the fans up. Otherwise, the fans are always running at their slowest speeds (around 800 RPM I think).

 

However, when doing a blend test in Prime95, my readings for the CPU are 57c-60c, no matter if the H100i is in quiet or performance mode.

 

This is because the water temperature is all that matters. Prime95 will take a while to make your water temp climb. You can watch it in real time and you'll notice it go up by 0.1°C every so often. It might take a minute or so to climb one full degree. In any case, the longer you let it run, the more your water temp will climb. This is the point when fan speeds can make a difference. It's up to you to decide what water temp provides acceptable CPU temps and then figure out which fan speed keeps the water in that range (without driving you mad).

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