What Exactly Happens When a Laptop Boots Up?

Dear ....,

When you start your computer first it will test the memory(RAM) and IO. Initially the processor has address 0000:0000 (for 16bit processor) in its address register so it fetch the instruction form this location of the memory only. there is a ROM chip on this location which contains the BIOS (Basic Input Output System) program. This BIOS program will start running first and it will detect and initialise all the Input and Output device, RAM and other peripherals. It will load the IVT(Interrupt Vector Table) for all this hardware and basic driver in the RAM. After that it will detect the 0th sector on Boot drive(Hard disk) and Load the files of OS into the RAM and hand over the control to OS. This all determined by the architecture of the computer not only by the chip(Microprocessor) the computer running (Pentium-III, IV etc). And because of this architectural difference the OS designed for IBM-PC does not work for Mac. Mac has a different architecture and I don't know much about the Mac.

You asked!

It generally works like this. The BIOS chip contains information that tells the CPU where to access the KERNEL (simple OS). It has information about the boot order and type of devices that may contain the OS. Once the KERNEL is loaded into memory, it takes over from there. The CPU just processes instructions. The OS program tells the processor what to do and when to do it. The speed of the processor will have an affect on the timing but there are instructions in the OS that affect this as well.