I am also confused a little. The propriety BIOS runs in the real mode, how does it test the memory beyond 1MB?
Another question is BIOS ROM can attach to XBUS, LPC, someone told me, even PCI, how dose the address forward to the location? Best Regards ??? Feng Libo @ AMD Ext: 20906 Mobile Phone: 13683249071 Office Phone: 0086-010-62801406 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Juergen Beisert Sent: Wednesday, May 30, 2007 6:09 PM To: [email protected] Cc: Fu xiayin Subject: Re: [LinuxBIOS] Question about protect mode? 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 -- linuxbios mailing list [email protected] http://www.linuxbios.org/mailman/listinfo/linuxbios -- linuxbios mailing list [email protected] http://www.linuxbios.org/mailman/listinfo/linuxbios
