Windows 10: CMOS Light Behavior

  1. Posts : 378
    Windows 10 Home April 2018 Update 64-bit
       12 Feb 2018 #1

    CMOS Light Behavior

    Ever since turning off Windows fast startup under power setting the CMOS blue light on my motherboard is on when my computer is off. The light turns itself off when I turn the PC back on. I'm just wondering if this is normal? I've always had fast startup enabled, but since it's messing up some driver initiliazation upon start, giving me a few errors and generally it doesn't do anything "fast", I turned it off and this is when I noticed the blue light. If I turn fast startup back on it's not there when I shut down my computer. Thank you.
      My ComputerSystem Spec

  2.    12 Feb 2018 #2

    May be because fast startup is a form of hybrid sleep. You will probably find that the CMOS light is on with fast startup disabled as an indicator that the motherboard is still getting power (albeit very, very low).
      My ComputerSystem Spec

  3. Posts : 378
    Windows 10 Home April 2018 Update 64-bit
    Thread Starter
       12 Feb 2018 #3

    That's what I'm thinking aswell, so I guess it's normal? I have a hard time finding any real documentation on this though. Seems like each mainboard behaves differently on when to emit the CMOS light.
      My ComputerSystem Spec

  4. Posts : 4,997
    Win10 Home and Pro, Win10 Insider Preview, WinXP Home Premium, Linux Mint
       12 Feb 2018 #4

    Don't know about blue but have seen red, green and amber and are related to power. The ATX motherboards have power connected to them continuously from the power supply when they are plugged into an AC source [or a UPS]. The power switch completes a circuit that tells the motherboard to wake things up and start the boot process. The older AT motherboards weren't like that, the power switch connected directly to the power supply itself, pressing the switch then got power going to the motherboard and devices.

    When changing cards, memory modules, etc., on an ATX board it is not enough to simply turn the computer off, have to pull the power cord and wait until that light goes out [or maybe press the switch] before removing/replacing things. This process assures any residual power is drained from the motherboard first.
      My ComputerSystem Spec

  5. Posts : 378
    Windows 10 Home April 2018 Update 64-bit
    Thread Starter
       12 Feb 2018 #5

    I have two green lights that shows the power symbol aswell as a reset that's close to the back near my PSU. Power is on all the time, reset is there when the PC is turned on. Then I have a blue light that's closer to the front of my case, guessing this shows power of some kind? This is on when my PC is on. Then I have another blue light at the back of my PC close to the I/O ports, this is the one I'm talking about. All these lights are confusing to me Maybe it isn't the CMOS then, what could this light be? It's only there when the computer is turned off and when fast startup is disabled.

    EDIT: According to my manual it's "Clear CMOS Button" I'm thinking of. Why on earth is that emiting?
      My ComputerSystem Spec

  6. Posts : 4,997
    Win10 Home and Pro, Win10 Insider Preview, WinXP Home Premium, Linux Mint
       12 Feb 2018 #6

    Your board must be quite newer model.
      My ComputerSystem Spec

  7.    13 Feb 2018 #7

    Your MB manual shows you have green/blue LEDs showing which of the dual BIOS options are in use and a power LED which is illuminated or blinking depending on the power / sleep status. I suggest you read your manual to work out what's happening. The power LED may always be on since the MB is powered by a +5V standby supply from the PSU even when the PC is off. The LED will only extinguish if you turn off the PSU using the switch on the PSU or turn off the PC at the mains plug.
      My ComputersSystem Spec

  8. Posts : 378
    Windows 10 Home April 2018 Update 64-bit
    Thread Starter
       13 Feb 2018 #8

    OK, I think I know what's going on. The blue light is supposed to be on in case I need to clear my CMOS, and is only on when the computer is off and when power is connected through it. The button light is there to remind me I guess. It doesn't light up when fast startup is enabled because, as stormy13 put it, it's kind of a hybrid sleep as it stores information on the disc before shutting down. I assume this method makes my board think that my PC is still on. I'm going to read trough my manual later today to verify this.
      My ComputerSystem Spec


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