1MB is a magic number. It works with advanced format disks, traditional disks, some odd SSD and most raid configurations.
Lucas Holt On Sep 21, 2011, at 4:26 AM, "Thomas Mueller" <mueller6...@bellsouth.net> wrote: >> From "Matthew D. Fuller" <fulle...@over-yonder.net>: > >> I've been meaning to mention this, but we really should document >> somewhere that it has a _MAXIMUM_ size. > >> I setup a system a few weeks back with GPT, and figured I'd just make >> the first 'real' partition start at the 1 meg mark. And make >> everything before that (1 meg - the however many sectors for the pmbr) >> the freebsd-boot partition. > >> It worked fine, up 'till the point that I tried to boot, and it >> completely failed to, complaining that the boot code was too big. I >> had to track around in pmbr to find > >> . . cmp $0x9000,%ax.. . # Don't load past 0x90000, >> . . jae err_big.. . # 545k should be enough for >> . . mov %ax,%es.. . # any boot code. :) > >> and redo the partition to 512k (leaving a few hundred k unused before >> the next partition started) before it would boot. That's a little >> nerve-wracking to hit on a critical system... > > I don't think there is any particular advantage in aligning GPT partitions on > 1 MB boundaries. > > Nothing sacred about being an integer power of 2, wouldn't it be sufficient > for boot partition size to be divisible by 4096 bytes, when the hard drive > sector size is 4096 bytes? > > > Tom > > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org" _______________________________________________ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
