CMOS Error and Boot Sequence Mystery

[petzoldt01]

I still don't know how this happened (even after I fixed it). Maybe someone else can enlighten me.

I have a multi-partition setup with grub2 as my bootloader. I restart my computer and it fails to POST ?!?!?!?! (black screen and freeze with NO feedback)

I remove the battery for a while, plug it all back up.
Finally get a BIOS warning, CMOS memory was corrupt; assumes default settings.

MYSTERY: Master boot record on my hard drive is now also corrupt?

Any method of attempting to boot from my primary hard disk failed. Had to rescueCD my grub2 setup, and then it works like a charm.
How does default CMOS = defunct grub?

My best guess is that CMOS stores an exact memory location on the disk, and that location was lost. I always thought CMOS pointed to &x00000000 on disk(0). Perhaps not.

Anybody else know what happened?

[jonzobrist]

Many BIOS default to IDE instead of AHCI for their SATA drives. Go into your BIOS and try toggling to the other one. They are not compatible, and changing them would look very much like hard drive corruption.
SNIP

[rubberman]

That's about what I would say... Once you have to clear the flash memory, boot back into the BIOS and make sure it is properly configured before you continue to boot the system.

[petzoldt01]

At that time, I was thinking similar. I remember trying several BIOS configurations, from defaults to my optimal config; no configuration changes made a difference. My current working settings were broken before I made the soft changes.

My fix started with changing the boot sequence to jump off the CDROM before HDD. Then boot the CDROM into my rescueCD. Odd thing is that rescue could properly mount and access my hard drive. Yet, any attempts to boot from the HDD directly from rescue were failed. Cold boots were failed. Also, not only did boots fail on the HDD, its more like the boot was hanging?!?!? There was NO MESSAGE saying 'Operating System not Found'. Just eternal darkness...

So, recap...
Corrupt CMOS = broken MBR.
All fixed with a simple 'grub-install' from the rescue.

I just dont understand how a corrupt CMOS made changes to the MBR (all indications lead me to believe my problem was related somehow to MBR).

P.S.
Maybe you guys are more right than I think... maybe BIOS configs were wrong somehow, but grub-install was smart enough to realize the error and correct it? (I am still sticking to my guns somewhat: grub-install fixed the problem)

[opalios]

howto manage mh grub loader in a multi boot system(vista-ubuntu 10.04-ubuntu 11.10)?None selection oprions during booting...