[LinuxBIOS] LinuxBIOS messing with CMOS on reboot?

Stefan Reinauer stepan at openbios.org
Sat Dec 3 23:21:56 CET 2005

* Eric W. Biederman <ebiederman at lnxi.com> [051203 22:28]:
> > 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.
Good point. I will try that to see if it changes the behaviour

> There are a couple of possibilities.
> - cmos_util needs to be explicitly told not to do the linuxbios checksum
>    calculation.

i've used file_to_cmos and cmos_to_file to switch. This should not do
any checksumming at all..

> - cmos_util has had problems when asked to flash all of the cmos options.
>   (Sigsegv ...) 

it seems to work fine. 256 bytes (which should be less as an option,
because I don't necessarily want to set back the clock) Also, rereading
the file after amibios corrected the checksum presents an identical file
(only the time changed)

> - 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.
It's an AMD k8 chipset. I wondered whether I failed to look at even
higher cmos values via 74/75 or something. but then again, LinuxBIOS
never touches anything except the low 128 bytes.

> And of course other mystic locations but I would exhaust the other possibilities
> first.
Power toggling seems a good start. Closed source proprietary software
sucks for customers. Unfortunately it might rather make them think in terms
of "bios is always complicated"


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