[LinuxBIOS] LinuxBIOS messing with CMOS on reboot?

Eric W. Biederman ebiederman at lnxi.com
Sat Dec 3 22:28:51 CET 2005

Stefan Reinauer <stepan at openbios.org> writes:

> Hi,
> I'm seeing a weird problem while switching back and forth between 
> a legacy bios and LinuxBIOS.
> I have a 256 byte cmos image created with cmos_util and a 512k bios
> image for each firmware flavour. 
> Switching from legacy bios to LinuxBIOS works fine using flashrom and
> cmos_util.
> Switching the other way round always leaves legacy bios with a wrong
> checksum on the first boot.
> writing the cmos from the file afterwards and rebooting is fine, so it's
> not the cmos image that is wrong.
> Could LinuxBIOS change the CMOS when doing a reboot?

Possibly.  The only safe way after a bios flash is to toggle the power.

> Or is legacy bios doing some very weird things like safing additional
> data in mystic places?

There are a couple of possibilities.
- cmos_util needs to be explicitly told not to do the linuxbios checksum
- cmos_util has had problems when asked to flash all of the cmos options.
  (Sigsegv ...) 
- The high 128 bytes are only moderately standard so it may be you have
  a board that stores them differently.  We should be ok for intel and
  amd chipsets.

And of course other mystic locations but I would exhaust the other possibilities


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