Bootloader - the first 512 bytes

[Gijs Slijpen]

Hello,

For a while now I have been trying to get a boot loader written in Assembly to 
work on a Dell Gateway 5000 and a Dell Latitude 5590 both have intel i5 
processors. My boot loader is a simpel one: it outputs the words "Hello World" 
to the screen. The code works in a virtual machine that I have set up in 
Virtual Box. However, when trying it out on a both of the machines mentioned 
before only “Hell” is being printed (maybe my computer is trying to tell me 
something). 

I figured out that if I use some padding in my boot loader right after the 
first command (for example defining 24 bytes of 0) and then continue my code 
the boot loader actually works on both my Dell machines but I do not know why. 
Then, just today, I thought I’d have a look at the Grub boot loader boot.S file 
to see whether I could get that to work on my Dell machines. Funny thing: I 
found there are 25 nop’s in there right after the first instruction. 

Would anyone maybe care to explain why this is? I have been looking around and 
not been able to find any documentation on this yet, there is a chance that I 
will find it in Intel’s software development manual but I thought I’d also ask 
it here.

I am looking forward to a reply.

Thanks in advance!

Best regards,

Gijs Slijpen