Problems with ATA_CAM support in RELENG_8

Jeremy Chadwick freebsd at
Wed Jun 30 21:21:40 UTC 2010

On Wed, Jun 30, 2010 at 04:52:22PM -0400, Paul Mather wrote:
> I thought ICH8 supported AHCI, but maybe it's only ICH8R that does?

No, not necessarily.  There are ICHxx (non-ICHxxR) models which
definitely provide AHCI (ex. ICHxxM for their Mobile chipsets; yes, many
laptops do have AHCI capability).  Thus there are many different
sub-models of ICH8, in addition to different perf/chip revisions of
ICH8.  Specification details:

Dell very likely chose not to engineer this particular motherboard to
not provide AHCI capability (Option ROM space (usually included with the
system BIOS), PCI and ICH8 register setups (done by the BIOS), etc.)).
I know Gigabyte has done this with some of their boards as well.

If you have concerns that your motherboard provides features that you
can't use, you need to contact Dell.

> I'm assuming that "subclass = ATA" means the controller can't operate
> in AHCI mode.  The BIOS setting is also confusing.  It has two
> options, "Normal" and "Legacy."  "Normal" mode says, "The hard drive
> controller is configured for native mode.  This mode provides the
> highest drive performance and most flexibility."  I guess I
> misinterpreted "native mode" to be AHCI mode.

"Native", "Normal", and "Enhanced" are all terms used to describe the
controller operating in standard SATA (non-AHCI) fashion.  Dell's
in-BIOS description is nothing but schmooze; it's not the same as AHCI.
"Legacy" just means the controller appears and operates purely in
PATA-esque mode, so that you can use SATA drives on systems which don't
have SATA chipset drivers (ex. MS-DOS).

To get an idea of what an AHCI-capable board offers via the BIOS, you
should review the following manual for a Supermicro ICH7-based system.
This chipset is older than yours, chosen for sake of example.  See
Chapter 7-3, section "Main Setup Features":

Furthermore, I can assure you that the Dell OptiPlex 745 Mini-Tower
offers AHCI capability, and toggling its use via the system BIOS.  You
won't find it mentioned in Dell's "Tech Specs" PDF about this though.  I
realise this is not the system you have, but I'm simply pointing out
that it's a board manufacturer decision whether or not to provide the
capability, and that their decision obviously changed over the years.

| Jeremy Chadwick                                   jdc at |
| Parodius Networking              |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |

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