Configuring H100i v2 on Linux

[eera5607]

Hi everyone. I've been reading a lot about H100i v2 and Linux compatibility issues. I know that in some cases the pump isn't running at an adequate speed (some people say the default speed is the slower possible). Since us, the Linux users, can't install Corsair Link the configuration is limited. I understand that in some cases the motherboard model can help to mitigate some issues and this is why I created this thread, to ask what would you recommend in the cases I will present. I decided that since the Linux support is limited I won't use at the moment some scripts or implementations published on different forums and therefor I won't use the Corsair Link Cable. 

Option 1: Asus Maximus IX Code and similar motherboards have a set of 7 - 9 headers to connect all thing related to cooling. See image below. 

The first option is follow the user's manual and connect the pump directly to the CPU_FAN (Q-Fan Controlled) header and the fans to the two connectors coming off the pump. In this case I think the pump speed will depend on the CPU temperature and fans will run at a constant speed (determined by what? default speed?) Is that correct? Following the instructions here I would configure full voltage from the BIOS to CPU_FAN.

Option 2: Taking into consideration the information in the image below:

What about connecting the pump to the AIO_PUMP header and the fans directly to the two connectors coming off the pump? Since the default speed in that header is "Full speed" will the pump run always at max speed and the fans at the same default speed of option 1? In that case we will probable get a boot warning, depends on the motherboard and BIOS (no CPU_FAN connected). 

Option 3: What about connecting the pump to AIO_PUMP and the two fans directly to the CPU_FAN and CPU_OPT? In that case we won't get a boot warning and the pump will work at full speed and the fans will run at variable speeds depending on the CPU temp. Is that correct? Remember that CHA_FAN's and CPU_FAN and OPT headers can be configure from the BIOS.

What other ideas do you have? Maybe connect the the pump to a CHA_FAN header? 
What is the best option? Thank you very much for your help. 

Sorry for the grammar and other mistakes, English isn't my native language. 

[For Science!]

6 minutes ago, eera5607 said:

-snip-

Glad to see a fellow linux user =)

 

So there are a few considerations, I assume you have a KabyLake i5 and i7, so your CPU is probably pretty hot. (This will influence your choice, see below).

 

I would recommend Option 1 in your case. Have the Pump header plugged into the CPU_FAN header, and then plug the two fans into the fan headers coming from the pump. It is very important however that you set the CPU_FAN to full speed mode (100% at all times) on DC mode in the UEFI BIOS.

 

This means that (positive):

-Your pump will be spinning at the correct speed at all times (the H100i v2 expects a constant 12 V supply)

-Your fans will react accordingly to water temperatures by the default fan curve stored in the H100i v2

  This is highly desirable since Kabylake is really hot and can easily exceed 75 degrees if not delidded

-You will not have CPU Fan Error since the pump will give a suitable reading

 

However this will also mean that:

- You cannot set up a custom fan curve (but see below why this is basically not possible anyway)

- 

 

Option 2 is kind of the same thing, however you will need to set your CPU_FAN "monitor" to ignore within the UEFI BIOS otherwise you cannot boot in. Alternatively plug a chassis fan into the header, but then in this case I would recommend simply option 1.

 

Option 3 is what I thought was good to begin with (And had my system like this until I realized next), but let me explain why it won't give you what you want. There are no headers within the motherboard that can read the water temperature of the AIO, and therefore all fan curves will obey CPU core temperatures. In watercooling, the cooling potential is completely dictated by the water temperature within the loop - simply put, if the water is room temperature, no matter how fast you spin the fans, the cooling will not improve i.e. there is absolutely no point in increasing the fan speed if the water is not hot. Ramping fan speed according to the water temperature is really the only fan curve that makes sense in any watercooled scenario.

 

Now comes a problem with the 6th and 7th generation intel processors, where the bad TIM between the die and the IHS means that the core temperatures easily goes above 75 degrees even if the water may be 30 degrees. Now, most of the ASUS boards have safety fan curves where the fans ramp up automatically to 100% when the cores hit 75 degrees. So I found myself in a situation where no matter how you set up your curve, the fan ramps up to 100% even if the water is cold, simply because the chip was thermally bottlenecked by the TIM. This is why it is actually simply impossible to set up any kind of sensible curve based on core temps (and as I explained above, it doesn't make any sense).

 

This means you are at the mercy of the default fan profile vs water temperature, but I found the default curve stored on the firmware adequate to keep the system cool even for scientific applications.

 

TL;DR - Option 1 but set your CPU_FAN header to DC mode and constant 100% (full speed)

 

 

 

[eera5607]

Thank you very much for this complete answer. My processor is an Intel i7 7700k.

Quote

In watercooling, the cooling potential is completely dictated by the water temperature within the loop - simply put, if the water is room temperature, no matter how fast you spin the fans, the cooling will not improve i.e. there is absolutely no point in increasing the fan speed if the water is not hot.

I didn't know that. That is very interesting because as you well explain the fans don't have the capacity to cool down the water since this is not and AC system or something like that. I hadn't thought that. 

About the Option 1:

Quote

Your fans will react accordingly to water temperatures by the default fan curve stored in the H100i v2

That was one of my main worries. I didn't know that the H100i v2 had a default curve stored internally that was used even without the Corsair Link software installed. Maybe the people that are having very low RPM's are not configuring the mobo via BIOS to deliver the 12v, always, as the default option depends (at least in my motherboard) on the CPU temperature to deliver the voltage dynamically to the header. As far as I understand.

 

So, in summary, the best option is to follow the user's manual and connect the pump to the CPU_FAN (configure the header to deliver full voltage always(12v)) and the fans to the pump to take advantage of the water temperature sensors installed on the system. That should work fine in most builds. 

 

Once again, thank you!