Re: BIOS startup ??

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On 8/19/07, Michael Harpe <mharpe79@xxxxxxxxx> wrote:
> The things that happen at power-up on most any modern computer are pretty
> much the same. It's dictated by the need to start in an orderly, known
> fashion every time. The idea of bootstrap programs go all the way back to
> the very early days of computers.
>
> When you push the power button, the system power supply control logic senses
> the closed switch and starts powering up the motherboard. On the motherboard
> there is logic that brings up the chips on the board in the proper sequence.
>
> Once the CPU is powered up properly, the logic on the chip senses that a
> power on reset has occured. The CPU logic is setup in a specific way such
> that the chip starts in a prescribed manner each time. This is the key to
> the whole process.
>
> What happens next varies by according to the individual chip architecture
> but in general this is where the BIOS gets involved.
>
> The BIOS (BIOS means Basic Input Output System) resides in a EEPROM or FLASH
> EPROM on the motherboard. This chip contains the program that gets the
> machine started along with the low-level routines that interface the
> operating system with the hardware on the motherboard. The CPU starts by
> loading an address from the last (or first) few bytes of this ROM and
> jumping to that address thus starting the boot process.
>
> What happens next is implementation dependent but basically consists of
> setting the machine up to run an operating system and then loading the boot
> block off of the selected boot device. This is usually the very first sector
> of the hard disk.  Once this is completed the same thing happens again, the
> BIOS loads the program into RAM and jumps to it.
>
> Now we're into the loader for the operating system. The loader does more
> preparation for running the OS and loads more of the OS into RAM. The next
> step loads what's called the kernel, which is the core operating system.
> From here you're running the operating system, be it Windows, Linux,
> whatever.
>
> I hope this helps!
>
> Mike Harpe, N4PLE
> Sellersburg, IN
>

If you want to know more try this site: http://computer.howstuffworks.com/
How a BIOS works is presented in this article:
http://computer.howstuffworks.com/bios.htm


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