amd64 native boot loader?

Joshua Isom jrisom at
Sat Dec 22 12:08:39 PST 2007

On Dec 22, 2007, at 3:32 AM, Bruce Cran wrote:

> AMD64 CPUs are backwards compatible with i386; they boot in 16-bit 
> real mode and only get switched into 64-bit 'long mode' by the kernel 
> later on. Since both i386 and amd64 start booting in the same way, 
> there's no need for separate bootloaders.
> --
> Bruce

I've thought about this too, but do wonder why the boot loader couldn't 
go into long mode in one of the loader stages.  I don't know if there'd 
be any significant improvements or drawbacks other than duplication of 
some code(which I imagine isn't changed often).

Somewhat offhand, can the OpenBSD loader chain boot FreeBSD?  Due to my 
dvd drive being sata over atapi, it wasn't recognized by the 6 branch 
until recently(many thanks to whoever committed the change).  But I 
recall that the boot cd for FreeBSD wouldn't boot, but the boot cd for 
OpenBSD would.  Of course that does primarily relate to cdboot and not 

More information about the freebsd-questions mailing list