On Friday 22 December 2006 01:02, Mike Doty <[EMAIL PROTECTED]> wrote about 'Re: [gentoo-amd64] Re: Emerging package as both 64 and 32 bit': > Duncan wrote: > > Simon Stelling <[EMAIL PROTECTED]> posted [EMAIL PROTECTED], > > > > excerpted below, on Mon, 18 Dec 2006 12:22:24 +0200: > >> Neil Bothwick wrote: > >>> What's wrong with the GRUB source package? > >> No problem, but it's 32bit. > > Indeed... for backward compatibility, amd64/x86_64 boots in 32-bit > > mode. Actually, I /believe/ it boots in 16-bit real mode, just like an > > x86, [...] but AFAIK the difference between compiling 16-bit and 32-bit > > code is simply a few compile-time switches, so it uses a standard > > 32-bit toolchain. > You're referring to real mode(16 bit). the BIOS will load the > bootloader in real mode, the bootloader will switch to protected mode(32 > bit) and if you have the right kernel, it will switch to extended > mode(64 bit)
Also, it's technically possible for the bootloader to switch into extended mode before loading the kernel, but not done (in GRUB, at least) for solid technical reasons. (IIRC, there's some memory mappings that have to be set up before entering extended mode.) -- "If there's one thing we've established over the years, it's that the vast majority of our users don't have the slightest clue what's best for them in terms of package stability." -- Gentoo Developer Ciaran McCreesh
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