When the power first is turned on the system clock begins to generate clock pulses First Step The CPU begins working and initializes itself resetting its internal values Second Step The CPU turns to memory address FFFF0h which is the memory address always assigned to the first instruction ID: 464290
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Slide1
POST AND ASSIGNMENT OF SYSTEM RESOURCESSlide2
When the power first is turned on, the system clock begins to generate clock pulses.
First StepSlide3
The CPU begins working and initializes itself (resetting its internal values).
Second StepSlide4
The CPU turns to memory address FFFF0h, which is the memory address always assigned to the first instruction in the ROM BIOS startup program.
Third StepSlide5
This instruction directs the CPU to run POST
Fourth StepSlide6
POST first checks the BIOS program operating it and then tests CMOS
RAM.
Fifth StepSlide7
A test determines that there has been no battery failure.
Sixth StepSlide8
Hardware interrupts are disable. (This means that pressing a key on the key-board or using another input device at this point does not affect anything.)
Seventh StepSlide9
Tests are run on the CPU, and it is initialized further.
Eighth stepSlide10
A check determines if this is a cold boot. If so, the 16KB of RAM is tested.
Ninth stepSlide11
Hardware devices installed on the computer are inventoried and compared to configuration information.
Tenth StepSlide12
The video card is tested and configured. During POST, before the CPU has checked the video system, beeps sometimes communicate errors. Short and long beeps indicate an error; the coding for beeps depends on the BIOS. After POST checks and verifies the video controller card (note that POST does not check to see if a monitor is present or working), POST can use the monitor to display its progress.
Eleventh StepSlide13
POST checks RAM
by writing and reading data. The monitor displays a running count of RAM during this phase.
Twelfth StepSlide14
Next, the keyboard is
checked (if you press and hold any keys at this point, an error occurs with some BIOSs). Secondary storage devices (including floppy disk drives and hard drives), ports, and other hardware are tested and configured. The hardware that POST finds is checked against the data stored in CMOS RAM, jumpers, and/or DIP switches to determine if they agree. IRQ, I/O addresses, and DMA assignments are made; the OS completes this process later.
Thirteenth StepSlide15
Some devices are set up to go into sleep mode to conserve electricity.
Fourteenth StepSlide16
The DMA and interrupt controllers are checked.
Fifteenth StepSlide17
CMOS setup is run if requested.
Sixteenth StepSlide18
BIOS begins its search for an OS.
Seventeenth stepSlide19
Hope you found this educational.
THE END