Grub and getting into Real Mode (low level assembler question)

Question

I've been working on a toy OS and have been using grub as my boot loader. Recently when trying to use VGA I found that I couldn't use hardware interrupts. This I found was because I had been slung into protected mode by grub.

Anyways the question boils down to - Does anybody know how to get back into real mode without having to get rid of grub?

Answer 1

This page explains all the dirty details. It's not easy. I did it once just for the kicks, and it was nasty..

http://www.sudleyplace.com/pmtorm.html

It's just to much to take care about to write as an short answer here, so I'll better give you a link.

Answer 2

Thanks, this looks more promising then anything else I've stumbled across.

Answer 3

If you are using GRUB as your boot loader you could use the intcall (as specified in the COMBOOT API) to call BIOS function int 0x10 in your case to access the VESA VBE.

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