simple question on fallback/normal images

steven james pyro at
Mon Mar 3 13:17:01 CET 2003


The fallback/normal all hinges on weather it's built with or in the southbridge. cmos_failover
looks at index 0x30 in the CMOS to decide if it should jump into the
normal image or not. It copies bit 0 to bit 1, zeros bit 0, and validates
the checksum. IFF the CMOS checksum is valid, the RTC indicates no power
failure and bit 1 (the value from bit 0) is set, it will jump to the
normal image. Otherwise it will fall through.

The checksum is just the summation of index 0x31 - 0x7d then
complemented. That is stored in 0x7e-7f.

So you can either set USE_FALLBACK_IMAGE and edit Config to use, or just don't set 0x30 bit 0 and the checksum.


On Mon, 3 Mar 2003, Ronald G. Minnich wrote:

> I need to build a bios for the clearwater with no fallback/normal images. 
> Just a single image. 
> I find myself unsure how to do this, I've not looked in depth at the 
> fallback/normal build stuff.
> Is there a simple option so I can build an image w/o the fallback/normal 
> stuff on systems like clearwater that are configured for fallback/normal?
> thanks
> ron
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> Linuxbios at

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