Date: Tue, 31 May 2005 16:56:49 -0400 From: John Baldwin <jhb@FreeBSD.org> To: freebsd-amd64@FreeBSD.org Cc: Michael Reifenberger <mike@Reifenberger.com> Subject: Re: 64bit loader Message-ID: <200505311656.50288.jhb@FreeBSD.org> In-Reply-To: <20050531165558.L88820@fw.reifenberger.com> References: <20050531133608.J87922@fw.reifenberger.com> <20050531143254.GC9158@dragon.NUXI.org> <20050531165558.L88820@fw.reifenberger.com>
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On Tuesday 31 May 2005 11:06 am, Michael Reifenberger wrote: > On Tue, 31 May 2005, David O'Brien wrote: > > Ha!! We can only have 1 sector worth of code in boot0. At this point we > > only have a few bytes of free code space. No where near enough to do the > > long mode switch. > > Sorry. I didnt meant boot0 but btx. I do know that boot0 is too small. > But btx is already switching to protected mode so it should be possible > to switch to 64bit mode too. Note that the loader uses the BIOS (via virtual 8086 mode) to do all the disk I/O, etc. Since long mode doesn't support vm86 mode, you'd end up with a loader that couldn't do any I/O to load the kernel, etc. unless you started including device drivers for all the different storage and networking hardware, etc. A 64-bit loader really isn't feasible unless your 64-bit machine includes firmware that you can use from 64-bit mode like EFI on ia64 or OFW on sparc. You probably want to stick with a 32-bit loader on amd64 for now. -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org
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