Class Eight Math Full Solution. pdf

4.5. BIOS Initialization Process 

There are five steps to the BIOS initialization process:
 Test some low memory.
 Scan for other BIOS.
 Yield to other BIOS,
 Inventory the system.
 Test the system.

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4.5.1. Test Low Memory 

In order for the BIOS to function, it needs some RAM to work with. So for most BIOS, one of the first things that get done is to test the bottom part of the system's RAM. Now, if that test crashes, then most BIOS can’t recover. 

4.5.2. Scan for Other BIOS 

The BIOS in your PC can't support every possible piece of hardware-LAN boards, unusual video hoards, you name it-and so the important functions of inventory and initialization have to go somewhere else. That is why many add-on boards have some ROM on them, as you may have noticed when installing boards. What you may not know is that those ROM contain some initialization code for those boards. For example, a hard disk controller ROM might do a quick read of the hard disk-kind of an "are you there?" test. A video board might test the memory on the video board. The main system BIOS allows the add-on boards to do their inventory and initialization first. Now, before that can happen, the main system BIOS must find those BIOS. 

4.5.3. Yield to Other BIOS 

Once it has found BIOS on the add-on board, the main system BIOS passes control to that BIOS so that it can do whatever inventory and initialization the add-on BIOS requires. The main system BIOS allows every add-on card's BIOS to initialize itself before doing its own inventory and initialization. Notice what that means: the software contained in the ROM on an add-in board gets to run before the system BIOS, and it also runs certainly before DOS gets loaded-we haven't gotten near to loading DOS yet. For an example, consider a VGA board. It has a BIOS chip on it, one that contains a setup routine. That setup routine announces that the board is up and ready by putting a copyright notice on the screen. 

4.5.4. Inventory and Test the System 
Once all of the add-in ROMs have gotten their time, and assuming that their programs ran properly and returned control to the main system BIOS, then the main system BIOS will now inventory the items that it will control, items that will vary from system to system. At minimum, one of the items that the system BIOS must inventory and initialize is the system memory. What does "inventory and initialize" mean here? You have seen at least one example of it -the memory test. Ever notice the quick flash of the drive lights on the floppy and hard disk drives? That's the inventorying of the storage devices. 

4.5.5. Loading the Operating System 
After the BIOS initialization process the microcomputer system is prepared to load the operating system. At first the BIOS loads a portion of the operating system then this loaded potion of operating system starts loading its remaining portion.