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After reading this lengthy article on UEFI and the recommendation to disable CSM for dual boot setups I went ahead and did so. Now I can't boot into UEFI-BIOS (normally pressing either Delete or F2 on boot).

A bit more info> Part of the problem may be my misunderstanding of what constitutes a 'dual boot' system.

Right now I have Linux and Windows, but they are each on totally separate SSD's and I only switch between them via the BIOS on boot. So technically I believe I have a single boot setup and shouldn't have messed with CSM.

To make matters worse, I attempted a BIOS firmware reset thru the Windows rescue menu, holding down shift on restart. Not sure what I did but didn't manage any BIOS reset or update and when rebooted get no video signal, just a black screen.

How do I get back into UEFI BIOS?

  • You disabled fast boot? or CSM? because these are 2 totally different concepts! – NetwOrchestration Dec 10 '16 at 3:27
  • Just don't worry ok? In my opinion, you haven't lost any files, you reset your firmware settings to default, and now EFI boot is disabled (I believe you have a CSM BIOS rather than a Modern EFI BIOS) Same happend to me, You just need to get into your BIOS and enable EFI boot again, and there are ways to do that. – NetwOrchestration Dec 10 '16 at 3:36
  • thanks, in my journey into Linux installs now feel I've broken everything that CAN be broken. Yes I know fast boot & CSM r 2 different things.Still need to figure out how to reset, or reinstall my UEFI firmware. Have done it before, but think that required first booting into UEFI! Bit of a chicken and egg problem. At least have resolved the black screen, my MOBO thinks I have 2 monitors when I have one...more digging. Maybe a way to reset UEFI thru command line? Or a switch on my AsusX99II-A MOBO? – Bachalo Dec 10 '16 at 13:59
  • wmic bios get /format:list give s brief summary of BIOS settings but nothing detailed and nothing CSM related – Bachalo Dec 10 '16 at 14:08
  • also tried this method to enter BIOShttp://www.dell.com/support/article/ca/en/cabsdt1/SLN143038 – Bachalo Dec 10 '16 at 14:15
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OP
I checked MOBO manual for ASUS X99A2- solution was to short 2 pins for 10-15 seconds after first shutting down and removing power cord. If someone knows of a software only solution...

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