Hi,
On Thu, Sep 22, 2011 at 4:43 AM, François Revol <re...@free.fr> wrote:
> Le 21/09/2011 21:25, François Revol a écrit :
> >
> > IIRC there is a convention that the MBR partition info (somewhere in the
> > sector buffer it just read) that the MBR handed control to is passed
> > over to the partition boot sector in a specific register.
>
> Replying to myself, we just had this discussion on IRC about it:
>
> 22:17 < phcoder> mmu_man: nearly no bootloader uses this info
> 22:18 < mmu_man> yeah, I know, I need to use it in Haiku someday :)
> 22:19 < mmu_man> would get rid of makebootable
> 22:19 < phcoder> mmu_man: beware that (a) in case of logical partition
> the info is difficult to use
> 22:19 < mmu_man> oh right
> 22:19 < mmu_man> :(
> 22:20 < phcoder> (b) some boot managers omit this information
> (especially some proprietary recovery stuff)
> 22:21 < mmu_man> and likely Haiku's bootman MBR
> 22:21 < mmu_man> how does DOS do it ?
> 22:21 < mmu_man> or does SYS.COM add the partition offset ?
> 22:21 < phcoder> mmu_man: there is a field in FAT BPB for this
> 22:22 < phcoder> it's misnamed "hidden sectors"
> 22:22 < mmu_man> aw
> 22:23 <@aljen> you mean ds:si pointing to selected partition entry in
> mbr when jumping into vbr's code ?
> 22:23 < mmu_man> yup
>
> Just so you know, seems not usable.
>
> François.
>
>
Thanks. I also agree. Though the MBR partition table contains the offset, in
the MBR code I read, it is not passed to the boot sector code of DOS. Thus
the boot sector of DOS needs to figure out where the partition locates on
the drive on its own. Usually the drive code originally set in DL by BIOS is
passed on by the MBR code. Please correct me if I'm wrong.
Best regards,
Robbie
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