UPDATE: ATA mkIII first official patches - please test!
Takahashi Yoshihiro
nyan at jp.FreeBSD.org
Thu Feb 17 00:08:47 PST 2005
In article <20050216.085534.128329712.imp at bsdimp.com>
"M. Warner Losh" <imp at bsdimp.com> 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 <nyan at jp.FreeBSD.org>
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