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Thread: Power On Self-test
2002-12-12, 21:41 #1
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- Jun 2001
- New York, New York, Lebanon
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Power On Self-test
<img src=/S/hello.gif border=0 alt=hello width=25 height=29> Loungers
Does any one know a good resource of information that describes the Power On Self-Test process?
I know that it checks the video and the IO devices and the RAM, and what have you, but in what sequence.
Also is that sequence BIOS related or is it standardized by now.
Thanks for any help.
Wassim<img src=/S/compute.gif border=0 alt=compute width=40 height=20> in the <img src=/S/bagged.gif border=0 alt=bagged width=22 height=22>
2002-12-12, 22:29 #2
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- Jan 2001
- Cincinnati, Ohio, USA
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Re: Power On Self-test
Unfortunately that varies from chip to chip. There is no real standard, but a typical POST sequence goes something like this:
[list=1]<LI>Display basic information about the video card - brand, video BIOS version and video memory available for example. The system's BIOS takes over the POST right after the video card BIOS.
<LI>Display the BIOS version and copyright notice in upper middle screen. You will see a large sequence of numbers at the bottom of the screen. This sequence is the BIOS identification line.
<LI>Display memory count. You will also hear tick sounds if you have enabled it.
<LI>In the majority of cases, the total of base memory and extended memory does not equal the total system memory. For instance in a 4096 KB (4MB) system, you will have 640KB of base memory and 3072KB of extended memory, a total of 3712KB. The missing 384KB is reserved by the BIOS, mainly as shadow memory.
The PCI bus will attempt an initialization of the Plug and Play cards and will display the card's name.
<LI>Once the POST has succeeded, you will see a basic table of the system's configuration. This usually includes interrupts and other information (status messages about DMI, ESCD). The BIOS then passes control to the boot sector of the hard drive, which loads the operating system.
There is also some interesting information at How Stuff Works, and there is a detailed explanation at this website. I once had a link to a nice graphical representation, but I can't find it at the moment. If I turn it up I'll post it here.