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I believe that my problem was caused by faulty CMOS battery that I didn't change for 5 months.

Every time I booted my laptop I was ask to set time/date. After extensive reading (I'm not an expert, only end user) it seems like NVRAM has its "x-times" write cycle and every time new UEFI OS is installed it's written as well.

My default Boot entries were hdd, USB, floppy, other USB, CD.

One day my BIOS "count cycle" greyed out & zeroed to "0000 times". At first I thought that some virus might cause that but do viruses have access to BIOS, don't know.

No matter what I do, removing CMOS battery, pressing every keyboard combination possible found on internet at boot, resetting BIOS to defaults etc, it never restores to my previous boot options in BIOS.

When I power on laptop I set date/time in BIOS when exiting I get warning

"Bootable device was not found" [continue], after pressing it, I get 2 options

-boot menu (which is blank) & -application menu with 2 other options

-BIOS setup & -diagnostic screen.

Entering diagnostic screen it discovers my hdd and USBs when plugged. But when I go back to BIOS boot options there is nothing but floppy disk. No way to boot from hdd or usb even though it's discoverable in diagnostics.

In this case (don't know for sure), did my NVRAM after being fully overwritten turned BIOS into some safe mode and erased all my boot entries?

BIOS type Phoenix SecureCore Tiano.

  • Did you replace that battery or not ? Please clarify as that is really important for the answer. – Tonny May 12 '18 at 18:17
  • No, I did not. Because I was planning on buying new laptop & thought that all the difference there was, was always setting time/date. I guess I was wrong. – juan May 12 '18 at 19:04
  • Found interesting read about NVRAM going read-only wilderssecurity.com/threads/… – juan May 13 '18 at 1:31
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Most BIOSs work similarly, so go into the BIOS setup you saw and make sure the hard disk and USB are set to enabled. It sounds like they are, but double check. Also in the BIOS menu, should be "boot options", or something similar. It should allow you to pick which devices are bootable and which order to look for them.

As for not being able to recover the settings, that is due to the battery being dead. All the configuration settings will be lost when power is lost. Thats why the battery is there, to keep those settings from being erased when power is out. Once those settings are gone, there is no recovery method to get them back.

  • Yes I spend two days educating myself, what is what. Doing all kind of different combinations. Everything that suppose to be enabled is enabled. All there is available in BIOS is floppy disk. What I don't understand is how come I managed 5 months on dead CMOS battery being able to run OSes and even boot from USB & suddenly it went berserk on me ? – juan May 12 '18 at 19:10

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