Re: [RFC] Restoring HDIO_GETGEO semantics (was: Re: workaround for BIOS / CHS stuff)

[Andrew Clausen]

On Sat, Jul 03, 2004 at 03:40:01PM +0100, Anton Altaparmakov wrote:
> > XP home edition (the green box)
> 
> Hm, I only ever tried XP Pro.

I guess we can try diff'ing the bootstrap code.  Should probably do this
in private for copyright reasons...

> > > Does it use NTFS as both the boot and system drive?
> > 
> > I am using a single NTFS partition.
> 
> I have lots of partitions (mostly Linux, NTFS is at end of disk).

If NTFS is at the end of the disk, doesn't it have to use LBA to address
it?

> > Note: I reversed-engineered the Windows FAT bootstrap code.  My analysis
> > is contained in the file doc/FAT in the Parted source distribution.  I
> > concluded that Windows uses LBA if the LBA flag is set in the boot
> > partition table entry.  (i.e. the partition type includes LBA in the
> > fdisk codes - this corresponds to a bit being set)
> 
> Interesting.  Maybe I don't have this bit set?

This bit only applies to FAT, AFAIK.  There is no corresponding bit
for NTFS.

> > > u16 sectors_per_track; /* Required to boot Windows. */
> > > u16 heads;             /* Required to boot Windows. */
> > > u32 hidden_sectors;    /* Offset to the start of the partition relative 
> > > to the disk in sectors.  Required to boot Windows. */
> > 
> > I just set the first 2 of these fields to 0, and everything still works.
> > Am I blessed?  (Or perhaps cursed!)
> 
> Odd.  Messing up any of the above three values makes my XP Pro fail to 
> boot!

Interesting.  How is your BIOS configured?  (LBA, Auto, CHS or Large?
what CHS values?)

Cheers,
Andrew