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Re: BIOS startup ??



William Case wrote:
> Hi;
> 
> I didn't want to steal a thread from someone who has a real problem, but
> an issue was raised in the thread entitled 'Grub' by Marko Vojinovic
> that has been bothering me for a long time.
> 
>         "And to my surprise, there the question was repeated, more
>         specific: "what happens between the points of pushing the power
>         button and the point when OS starts to load?" ;-)
>         
>         I was amazed !! The sequence of actions was explained in a way
>         that did not need any too technical background knowledge, while
>         at the same time it was extremely detailed. It started off along
>         the lines of "voltage on the circuitry rises, and the oscillator
>         starts ticking. The first few ticks activate a circuit that
>         sends a reset signal to the processor...".
>         
>         The moral of the story: it was way more complicated than I
>         thought, while the author was stating that the answer is
>         somewhat oversimplified..."
> 
> I have been trying to find that answer for some time now. 
> 
> What happens in the micro-seconds between hitting the power button until
> BIOS is loaded from CMOS into RAM memory?  There is lots of information
> available about what happens next.
> 
I believe that the way it goes is the processor is reset, and then
it starts executing the BIOS code. There is a circuit that holds the
processor in reset until the power supply has (hopefully)
stabilized. Depending on the system, and BIOS options, the BIOS may
never be copied into RAM. (At least, I have several systems that
have shadowing the BIOS in RAM as an option.) With the faster
EEPROMS and limited BIOS use of most modern OS's, I am not sure that
the BIOS is shadowed in RAM any more.

Mikkel
-- 

  Do not meddle in the affairs of dragons,
for thou art crunchy and taste good with Ketchup!

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