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 Post subject: int 10h bad working
PostPosted: Fri Jul 19, 2019 1:11 pm 
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Joined: Fri Jul 19, 2019 1:03 pm
Posts: 3
I have this code:
Code:
BITS 16

start:
   mov ax, 07C0h   
   add ax, 288      
   mov ss, ax
   mov sp, 4096

   mov ax, 07C0h   
   mov ds, ax


   mov si, text_string
   call print_string   

   jmp $   


   text_string db 'This is my cool new OS!', 0


print_string:   
   mov ah, 0Eh

.repeat:
   lodsb   
   cmp al, 0
   je .done   
   int 10h
   jmp .repeat

.done:
   ret


   times 510-($-$$) db 0
   dw 0xAA55


I build it with NASM.
It works on qemu, but not on my machine. Only 'This' is displayed.
I add that 0xB8000 also displays a bit of message.


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 Post subject: Re: int 10h bad working
PostPosted: Fri Jul 19, 2019 1:58 pm 
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Joined: Fri Aug 26, 2016 1:41 pm
Posts: 482
If you are booting using USB on real hardware you may be seeing this if your BIOS is booting using floppy disk emulation (FDD) and because you don't have a BIOS Parameter Block (BPB) in your bootloader. Likely your BIOS has blindly overwritten some of your bootloader with drive geometry info which has altered it so it doesn't work correctly. If this is a USB booting issue you may wish to read my Stackoverflow answer on the subject: https://stackoverflow.com/a/47320115/3857942


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 Post subject: Re: int 10h bad working
PostPosted: Fri Jul 19, 2019 2:44 pm 
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Joined: Fri Jul 19, 2019 1:03 pm
Posts: 3
Problem solved, thank you! It is worth to write about it on Wiki.


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