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During debugging a Linux boot problem, I disabled USB power on boot in the BIOS. This was effectively an irreversible change, since I can't enter the BIOS anymore now. My motherboard is Asus Z97-A. I can currently boot into Windows on this PC (Linux is #2 in the Grub menu, so I can't select it due to the lacking power to the keyboard). My keyboard is wireless, in case that's relevant. I don't have a wired keyboard.

How can I enter the BIOS so that I can re-enable USB power on boot? Is this possible to change directly from Windows? I tried the "Advanced start-up" from Windows, but "UEFI settings" was not visible in the advanced troubleshooting options when I restarted.

  • You can reset BIOS by taking out the battery. – Vojtěch Dohnal Jul 1 '16 at 7:53
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    I still keep a PS/2 keyboard around after all these years just for occasions like this. – Wes Sayeed Jul 1 '16 at 7:56
  • Or for use as main keyboard (Model M for the win!) – Hennes Jul 1 '16 at 8:00
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There are three possible ways to solve this:

  1. Make your motherboard forget its settings. (Take the battery out, see the many posts on BIOS resets)
  2. Borrow a wired keyboard.
  3. Find a tool which lets you edit the motherboards saved configuration. While in theory this is neat, it is also something with which I have no experience at all.

Personally I would go for #2. Simple, safe, and you do nto even have to buy one. Just borrow a keyboard for a day.

  • #2: Does it need to be PS/2? Wouldn't a wired USB keyboard also suffer from lack of power? – cmeeren Jul 1 '16 at 8:03
  • @cmreen That motherboard has one PS/2 port. – Vojtěch Dohnal Jul 1 '16 at 8:05
  • If the EFI setting disabled all USB power during boot: Then yes. Or rather, anything but USB. And you have two choices with that motherboard, one of which got disabled. That leaves old but very common PS keyboards. – Hennes Jul 1 '16 at 8:06
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Use CLR_CMOS button (if you have it on your MB version) when the PC is fully powered off to reset BIOS settings. http://www.hardwarezone.com.sg/review-first-looks-asus-z97-deluxe-nfc-wlc-motherboard

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Also it is possible to reset it by taking out the battery. Turn off the PC, take the battery out of your motherboard, wait few seconds, then put it back, then turn the PC on. This should reset your BIOS settings.

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  • Add a brief 'wait' after taking out the battery? – Hennes Jul 1 '16 at 7:59
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  • Use CLR_CMOS button on the bottom of your motherboard.
  • Remove CMOS battery, wait for around 15 secs. and place it back in its socket.
  • Use a wired keyboard (borrow, or keep one permanently for such emergencies)

There must definitely be an option(namely 'Auto') in the Boot tab of your BIOS, the PC disables the power on boot for all USB ports other than the ones in which the mouse and keyboard (only wired) are plugged.

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