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CPU fan error on boot


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I just built a new box, ASUS Maximus X Hero and installed the H115i (I've already got 4 other, older Corsair liquid coolers) and I get a CPU fan error on boot when I use the AIO header on the motherboard. Using the CPU Fan header its fine.

I've done hours of reading and most say just set the fan speed in BIOS or set to ignore but that doesn't work.

Bottom line, things look to work fine but ASUS suggests using the AIO when using pump coolers so what's up? How is this going to affect the Link software and/or Qfan in ASUS?

I'm usually a 'if it's working, don't change anything guy' but I don't build computers often so I've not really kept up with all the options and just want to keep it simple stupid.

Thanks in advance for your replies and help!

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First, there absolutely are no special properties whatsoever on Asus AIO or W_Pump headers. It is a plain old CHA fan header that is supposed to be preset to run at 100% fixed. This is further alleviated since the H115i does not draw power through the motherboard header - no matter which one you choose. All the power comes from the SATA line. The motherboard fan header will report half the actual pump speed (no overly useful) and will give you an instant notification if the pump fails during boot, but only if you have it on CPU Fan. None of the other headers have a boot warning feature.


I am going to take a leap and assume that when you were trying to use AIO header for the H115i, nothing was on CPU_FAN. That is the problem. Something always has to be on CPU fan or you will get the boot error. You can disable the warning, but that doesn't really address the issue. You have a bunch on less than full functional motherboard headers that don't have a flexible uses.


CPU Fan - must have something here to boot or get the error. CPU temp is the only control variable for fan speed. Very short fan delays (to prevent the fans from ramping up and down) and historically those delays are often ignored anyway. All of that make it a great place to park the H115i header, that does nothing and doesn't need power or control.


CPU OPT - this is a copycat of CPU fan. No direct controls of its own. Whatever CPU fan does, OPT copies and thus the same limitations. Meant to be used with dual fan air towers, although CPU/OPT can be used for the fans with cooler without an internal controller.


AIO and W_Pump - Fixed at 100% by default. No useful for fan control. However, if you go into the Advanced BIOS -> Monitor Tab -> Q-fan (way down at the bottom)... there should be an option to turn both of those back into regular fan headers with control. However, they will be limited to CPU temp only, so not as functional as a standard CHA fan header.


Frankly, we were all better off when the boards came with CPU/OPT and 4-5 CHA fan headers. A chassis fan header can be set to 100% too, along with multiple other things. Those AIO and W_Pump headers were not free. They are converted CHA headers with less flexibility.

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Well, that just makes too much sense! :) Really appreciate the info.

So, is it then suggested I put the 115i on the AIO and move the front fans to the CPU fan header?


I've got no problem using the Qfan software. On my older boxes, I set it once and haven't checked it in years. It just works. I don't overclock (well, the few times I have, it's been very little) and it appears ASUS has only improved on it but it looks as though it's no longer a Windows Program but in the BIOS.


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No, my recommendation is to put the H115i on CPU fan. This is the same as any other header, except if the thing has an electrical failing on boot (power on is always to most likely failure point for an electronic device), you will get an immediate reaction.


If you need more headers for case fans, toggle the switch in the BIOS to turn AIO and W_PUMP back into controllable headers. This gives you two more individually controllable headers (as opposed to one) and in my experience CPU fan often has some hidden behavior parameters that make it less than suitable for a case fan. It was designed to run an air tower fan.


The only reason to move the fans from the H115i to the motherboard directly is if you don't/can't run Link or iCUE for desktop cooler control. In that circumstance, BIOS fan control is better than none.

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