[flashrom] JIDA CMOS

Bill Flanders (wtflanders) wtflanders at micron.com
Thu Apr 8 17:46:14 CEST 2010

You are correct... We have no battery backup on our custom carrier board.

-----Original Message-----
From: Michael Karcher [mailto:flashrom at mkarcher.dialup.fu-berlin.de] 
Sent: Thursday, April 08, 2010 12:44 AM
To: Carl-Daniel Hailfinger
Cc: Bill Flanders (wtflanders); flashrom at flashrom.org
Subject: Re: [flashrom] JIDA CMOS

Am Donnerstag, den 08.04.2010, 04:20 +0200 schrieb Carl-Daniel
> > I ran into the same problem when I automated flashing the BIOS followed
> > by running nvramtool to set the CMOS values.
> > The settings do not hold if you power down the system, however, they do
> > hold when you reboot the system via the "reboot" command.
> So unless I'm misunderstanding you, the BIOS performs some "magic" on a
> warm reboot which causes the effect of nvramtool to become permanent.

As I understand it, the system is equipped with two storage system for
the BIOS parameters: The CMOS RAM/"RTC" and an "EEPROM" (which is why
you need to run jidacmos twice - one for rtc, once for eep). My guess
would be that this eeprom is a i2c eeprom that contains a copy of the
rtc parameters. The CMOS RAM seems to be powered down/lose settings on
powering down the system (i.e. no battery backup), so parameters are
restored from the EEPROM on next power-on.

  Michael Karcher

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