On Tuesday 29 May 2007 04:50, Fu xiayin wrote:
Hello,everyone. I'm a student, and now my task is studying Linuxbios.
I'm not very clear about the difference between the protect mode and the real mode.
Real mode: 16 bit offsets, address space limited to 20 bit. Protected mode (or "Linear Flat Mode", see below): 32 bit offsets, address space 32 bit
So I wonder why should Linuxbios turn into protect mode at the very beginning.
Try to access your ROM at physical address 0xFFFF0000 in real mode and you will "feel" the reason. ;-)
And is there any difference between protect mode in Linuxbios and in linux kernel. If any, what's the main difference?
The mode used in LinuxBIOS is more a 32 bit real mode (called "Linear Flat Mode") than a protected mode, because there is no protection at all. Also there is no paging and no address translation activated. Every segment starts at physical offset 0x00000000 and has a limit of 4GiB (this means: "no limit").
Juergen