BIOS startup ??

[Karl Larsen]

Michael Harpe wrote:
> The things that happen at power-up on most any modern computer are 
> pretty much the same. It's dictated by the need to start in an 
> orderly, known fashion every time. The idea of bootstrap programs go 
> all the way back to the very early days of computers.
    In my first job the computer was turned on every morning. It had a 
paper tape reader on front. There was a short tape called boot-up. This 
you put in the tape reader and started the computer. It read off the 
instructions on how to start from the tape.
>
> When you push the power button, the system power supply control logic 
> senses the closed switch and starts powering up the motherboard. On 
> the motherboard there is logic that brings up the chips on the board 
> in the proper sequence.
>
> Once the CPU is powered up properly, the logic on the chip senses that 
> a power on reset has occured. The CPU logic is setup in a specific way 
> such that the chip starts in a prescribed manner each time. This is 
> the key to the whole process.
>
    After the boot-up tape was done there was a much longer paper tape 
that got all the things working like a monitor and a keyboard.
> What happens next varies by according to the individual chip 
> architecture but in general this is where the BIOS gets involved.
>
> The BIOS (BIOS means Basic Input Output System) resides in a EEPROM or 
> FLASH EPROM on the motherboard. This chip contains the program that 
> gets the machine started along with the low-level routines that 
> interface the operating system with the hardware on the motherboard. 
> The CPU starts by loading an address from the last (or first) few 
> bytes of this ROM and jumping to that address thus starting the boot 
> process.
>
> What happens next is implementation dependent but basically consists 
> of setting the machine up to run an operating system and then loading 
> the boot block off of the selected boot device. This is usually the 
> very first sector of the hard disk.  Once this is completed the same 
> thing happens again, the BIOS loads the program into RAM and jumps to it.
>
> Now we're into the loader for the operating system. The loader does 
> more preparation for running the OS and loads more of the OS into RAM. 
> The next step loads what's called the kernel, which is the core 
> operating system. From here you're running the operating system, be it 
> Windows, Linux, whatever.
>
> I hope this helps!
>
> Mike Harpe, N4PLE
> Sellersburg, IN
    So even 50 years ago there was a boot-up method not a lot different 
than now.


-- 

	Karl F. Larsen, AKA K5DI
	Linux User
	#450462   http://counter.li.org.