In article <[EMAIL PROTECTED]>
"M. Warner Losh" <[EMAIL PROTECTED]> writes:

> I see.  Let me see if I understand the implications:
> 
>       (1) This disk won't interoperate with other OSes on the pc98
>           machine because the pc98 partition format specifies things
>           in terms of CHS, but doesn't specify an actual geometry.

I don't test it yet, but I think it is no problem if right geometry
translation is done.


>       (2) Further, since dp_scyl and dp_ecyl are both 16bits, we are
>           limited to 65535 cylinders.  The above geometry of 387621
>           violates this assumption.  So you can really only use
>           66059280 of the 390721968 sectors on this disk (or about 17%).

I tried to use the disk with 16H/63S geometry but I cannot at all.  It
seems that the fdisk and/or disklabel write to strange place.


>       (3) It is insufficent to fix this in geom_pc98 because that is
>           not used until after the partition is placed on the disk
>           and fdisk_pc98 needs the geometry to place that partition.

Yes.


>       (4) This only impacts newer ATA6 disks.  ATA5 and older appear
>           to be working properly.  ata6 disks need some other
>           mechanism to get this information, correct?

Probably...  I am sure that ATA6 disks at least need to get a geometry
information from PC98 BIOS.


> When I asked about the 'get the geometry from the BIOS' patches that
> are circulating, I was told that it was hard to match the FreeBSD
> device to the BIOS table.

I think that it is hard to get a right geometry in all cases, many
extended ATA cards are used, but it succeeds mostly.

---
TAKAHASHI Yoshihiro <[EMAIL PROTECTED]>
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