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Grub and transition to Real Mode (low-level assembler programming)

I work on a toy OS and use grub as my bootloader. While trying to use VGA recently, I found that I could not use hardware interrupts. I discovered this because I was immersed in grub protected mode.

Does anyone know how to return to real mode without getting rid of grub?

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assembly x86 real-mode grub
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If you use GRUB as a bootloader, you can use intcall (as indicated in the COMBOOT API ) to invoke the BIOS function int 0x10 in your case to access VESA VBE .

But this will not help if you need to access the hardware VGA registers.

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do you mean writeport (value, $ 3c9)?

 >mov 03c9,AH >out value,AL

or similar in INTEL asm (NASM)

3c9 3C8 IIRC - VGA registers.

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