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  1. #1
    ROG Guru: Yellow Belt Array
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    Using CPU OPT header for case fan

    Hi, is it a good idea to use the CPU OPT header to control case fans? I have gotten 4 CoolerMaster JetFlo 120 95 CFM fans for the four case fan slots on my case but I see my ROG Strix X470-F Gaming motherboard only has three fan headers for case fans. I dont want to use a splitter because these fans use a lot of power (0.4A) and I have heard reports that using splitters with them isn't a good idea. For the fourth case fan can I use the CPU OPT header or will that lock that fan to the voltage of the CPU fan (which is a different model, although I am considering getting a fifth JetFlo 120 fan for the CPU heatsink.) I really need to regulate the speed of these fans because at 100% they sound like a dozen vacuum cleaners all turned on at once! That's why I dont know if it's a good idea to put a case fan on the CPU OPT header if that header is locked to the voltage of the CPU fan or to get a fifth one for the CPU cooler, the voltage needs to be around 5V-7V (40%) on each fan to make the fan noise bearable.
    Last edited by Alex0915; 09-08-2018 at 10:13 AM.

  2. #2
    untouched Array Praz's Avatar
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    Hello

    The CPU OPT fan header is slaved to the main CPU fan header. Its control cannot be set independently of the the CPU fan header.

  3. #3
    ROG Guru: Yellow Belt Array
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    Thanks, just what I needed to know! So the CPU OPT header is better used for a push-pull configuration on a CPU cooler (although I don't even know if my CPU cooler supports that)? Do you think it would be good to use this kind of fan on the cooler or do you think it's way too loud and I would be better served with something quieter (since this fan has to be run at less than 50% to be bearable.) Sounds like using the CPU OPT header to run a case fan would not be a good idea since the CPU FAN usually runs at a higher voltage than the case fans on the Chassis header and the fans I am using are particularly loud and I want to keep them to as low a voltage as possible.

    Do you by any chance know what the minimum speed is that I can set my fans to on each of these headers- for example, can I get them down to 50% or less? I would think the Chassis fan headers are more flexible on the minimum speeds while the "system" automatically controls the CPU FAN and the CPU OPT header and manual control over that is not possible or not a good idea? Another question, is the amount of maximum power draw allowed on each header 1A, and does the same apply to the CPU FAN and the CPU OPT headers or do they share 1A between them since the CPU OPT header is a slave to the CPU FAN header? Thanks!
    Last edited by Alex0915; 09-08-2018 at 03:00 PM.

  4. #4
    ROG Guru: Yellow Belt Array
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    I was also just reading about the two PUMP connectors on my board (AIO and W) and I can use these for my case fans too? Does this mean I can connect two additional case fans and I can control the speed of the fans independently of other fans when connected to these? I also read that they handled a higher power, about 3A, unlike the 1A of the regular fan headers? But with each of these PUMP headers, if I do attach fans to them I can't control the fan speeds using software, but I can in BIOS and they aren't a slave to any headers?

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