[jmpeer]

Hi.
Uh, don't really know what this would go in.
So I thought by the nature of the question it belongs here.

After the bios is situated, in terms of memory, can someone summarize the boot process?
As far as I know:
It reads the first X many bytes - the boot loader.
Then it reads the boot sector of some OS - 512 bytes long starting at the address 0x7C00.
Then IDK.

Can someone just, elaborate, on the boot process in terms of memory like this?

[Martyr2]

Well the only job of the boot loader is to simply read a set of instructions into RAM. These instructions could be simple commands or small utility programs that vary depending on the OS. Once it reads it from the boot sector of the drive into RAM, it then executes those instructions which handles the rest with regards to loading device drivers, system files etc. Of course the instructions it runs are different for each OS. It may even load second stage boot loader programs.

So in addition to what you have already stated, it reads the boot sector, loads it into RAM and executes what it loaded. Then those files will launch the OS. Not much more to know really.

This post has been edited by Martyr2: 26 March 2010 - 10:40 PM

[calvinthedestroyer]

If I remember correctly the CPU reaches a READY state then it loads an instruction from &h100 (cmos) This starts the cmos firmware. The cmos firmware determines what the boot device is, then checks for an os and then boots that os.

In the older windows days the boot sector contained three files:
io.ms
msdos.sys
command.com

once those files were loaded you technically had an OS.

Ahh here's what I was thinking of:

Quote

Smaller computers often use less flexible but more automatic bootload mechanisms to ensure that the computer starts quickly and with a predetermined software configuration. In many desktop computers, for example, the bootstrapping process begins with the CPU executing software contained in ROM (for example, the BIOS of an IBM PC) at a predefined address (some CPUs, including the Intel x86 series are designed to execute this software after reset without outside help). This software contains rudimentary functionality to search for devices eligible to participate in booting, and load a small program from a special section (most commonly the boot sector) of the most promising device.

You should read this Wiki page about the Boot process: Booting and the boot strap process
Its pretty heavy reading so you might want to make a pot of coffee first

This post has been edited by calvinthedestroyer: 26 March 2010 - 11:23 PM

[debjit625]

As soon as you power your system the processor start executing the instruction on CMOS or ROM ,these instructions are called BIOS and what it does? it checks if all the peripheral connected to CPU are ok and responding to CPU i.e.. is the I/O is ok or not,if everything is ok then it goes for the next final step that is, to find a booting device (ex.. Hard disk) when it found one it reads the first sectors 512 bytes (normally) and load these data at 0x7C00 on memory(RAM)
then the CPU start executing the instructions from 0x7C00 .The data resides at the first sector of the booting device is nothing more than some instructions that could be read by the targeted CPU ,and its called Master Boot Record (MBR) and these instructions further loads the OS (ex.. kernel).However booting process is much more complex their are many good articals over net google them and offcourse have a look on Developers Manual provided by the vendors of CPU (like Intel,AMD).

Good Luck