Boot sequence of a standard computer

Posted on 2007-07-25
Last Modified: 2012-05-05
I am trying to figure out what the boot process is from POST to the actual start up of the OS on the computer.
Question by:matt_starkey31
    LVL 3

    Accepted Solution

    Here's a good breakdown I found a while back...
    LVL 32

    Assisted Solution

    This is an excerpt from the COMPUTERHOPE pages found here

    Each time the computer boots up the computer must past the POST. Below is the common steps a POST performs each time your computer starts.

       1. The first step of POST is the testing of the Power Supply to ensure that it is turned on and that it releases its reset signal.
       2. CPU must exit the reset status mode and thereafter be able to execute instructions.
       3. BIOS checksum must be valid, meaning that it must be readable.
       4. CMOS checksum must be valid, meaning that it must be readable.
       5. CPU must be able to read all forms of memory such as the memory controller, memory bus, and memory module.
       6. The first 64KB of memory must be operational and have the capability to be read and written to and from, and capable of containing the POST code.
       7. I/O bus / controller must be accessible.
       8. I/O bus must be able to write / read from the video subsystem and be able to read all video RAM.

    If the computer does not pass any of the above tests, your computer will receive an irregular POST. An irregular POST is often a beep code that is different from the standard one or two beeps. This could be either no beeps at all or a combination of different beeps indicating what is causing the computer not to past the POST.

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