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Ok, I've got my bootloader to load a kernel off a floppy, and it succesfully jumps to the kernel But I tried doing:

mov ax, 65
mov [0xb8000], ax

to print the letter A in the top left hand corner, but it doesn't seem to work. Do I have to access memory differently in protected mode? Thanks.

Hi,

Pulser wrote: Ok, I've got my bootloader to load a kernel off a floppy, and it succesfully jumps to the kernel But I tried doing:

mov ax, 65
mov [0xb8000], ax

to print the letter A in the top left hand corner, but it doesn't seem to work. Do I have to access memory differently in protected mode? Thanks.

There are major differences for memory access in protected mode (it's protected!). See Intels manuals for details...

Despite this your code may actually be working. It puts an 'A' in the top left corner of the screen with a black foreground and a black background. Because both colours are black it will all look black

Perhaps "mov ax,0x0F41" might work (it'd do the same but the foreground colour will be white). If it doesn't work then there's something wrong (or unexpected) with the way DS is configured..


Cheers,

Brendan

you of course turned on protected mode before trying this ? ...