[LinuxBIOS] Read / Write to CMOS

David Hendricks dhendrix at google.com
Wed Jan 24 00:49:11 CET 2007


The functions come from asm/io.h, 0x70 is the CMOS memory address I/O port,
and 0x71 is the CMOS memory data I/O port. It looks like
http://www.faqs.org/docs/Linux-mini/IO-Port-Programming.html has some good
information on this topic. I know "The Undocumented PC" by Van Gilluwe has a
pretty thorough discussion of the CMOS ports as well.

On 1/23/07, Ben Racher <mack.stout at gmail.com> wrote:
>
> ron minnich wrote:
> > On 1/22/07, mack stout <mack.stout at gmail.com> wrote:
> >
> >> Does linuxbios support altering bios settings from userspace?
> >
> > it's easy to do this.
> >
> > You need the simple tools that read and write cmos.
> >
> > Attached.
> >
> > ron
> perfect! just what I had been looking for, and it even works fine with
> phoenix award bios! I just set the settings that I want to change, dump
> it, and then write it to clients (with exact same hardware) and the
> settings are applied. amazing!
>
> now i just need to learn what actually happens in these 35 lines of code
> :-) what library does
> outb(regno, 0x70); come from? and 0x70 represents the memory where cmos
> starts at?
>
> ben
>
> --
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>
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