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 ri...
Let's say I'd like to start a small linux distro before my ordinary operating system start. BIOS load MBR and execute MBR. MBR locates the active partition which is my linux partition. Linux start and I perform what I need to do. Linux shut down and I switch to Real Mode again. The original partition boot sector is loaded and my ordina...
I'm trying to alter my interrupt table to take over the keyboard interrupt. My end goal is to write my new interrupt routine, copy myself into RAM and make the real-mode interrupt table point to me. I have found random sample code online but it is missing explanations on how to get the address of the original interrupt. They simply ha...
In real mode on x86, what instructions would need to be used to run the code on a different processor, in a multiprocessor system? (I'm writing some pre-boot code in assembler that needs to set certain CPU registers, and do this on every CPU in the system, before the actual operating system boots.) ...
mov al,10 add al,15 How do I print the value of 'al'? ...