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What happens between reset vector ad BIOS

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whitchurch85

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After i reset/ turn on my computer, CPU executes first instruction from reset vector( eg:- location 0Xffff ) now what happens after this.

How does the BIOS take over to perform its POST and pre-boot duties.???

I want to undertand what happens in the gap between the reset vector and the BIOS take over.

Does the reset vector point to the BIOS code, or is reset vector part of the BIOS code.
 

reset vector is in bios area.
so bios takes over on reset itself.
 
Thanks, for the info, i would like to get a more detailed book to get into more in this topic.

Any chance of knowing where i can get the following books as pdf:

Peter Abel IBM PC Assembly Language and programming

Rafiq Usman's famous Microprocessor book. I forget the title of this book.
 

The reset vector is at f000:ffff I think and it is inside the BIOS ROM itself.
Start up procedure is:
1. POST tests, at start of each test a number ("Checkpoint") is written to port 80 so a failure can be traced from the last number sent out.
2. Set up a default interrupt vector table, it might be modified later by other ROMs claiming them.
3. Initialize other ROMs, including the one on the video card, this is typically where you see the video manufacturers logo on the screen.
4. Attempt to load the boot sector to a fixed memory address. If successful, the loaded code is then executed and should in turn load the main operating system.

You can learn a lot by opening a terminal window and running the Debug program. When you have the prompt on the screen, type debug then '?' to get help.

Brian.
 
Thanks Brian for the detailed explanation, helps a lot. Especially about the debug mode

betwixt said:
The reset vector is at f000:ffff I think and it is inside the BIOS ROM itself.
Start up procedure is:
1. POST tests, at start of each test a number ("Checkpoint") is written to port 80 so a failure can be traced from the last number sent out.
2. Set up a default interrupt vector table, it might be modified later by other ROMs claiming them.
3. Initialize other ROMs, including the one on the video card, this is typically where you see the video manufacturers logo on the screen.
4. Attempt to load the boot sector to a fixed memory address. If successful, the loaded code is then executed and should in turn load the main operating system.

You can learn a lot by opening a terminal window and running the Debug program. When you have the prompt on the screen, type debug then '?' to get help.

Brian.
Click to expand...
 

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