AHCI/ATA_CAM for dummies?

Doug Barton dougb at FreeBSD.org
Mon Dec 14 20:47:16 UTC 2009

b. f. wrote:
> On 12/14/09, Doug Barton <dougb at freebsd.org> wrote:
> I believe what they meant in the Intel document was that in order to
> use certain features supported by AHCI, such as NCQ, the disk drive
> must also support them.  Your disk drive seems to support NCQ.

Ok, I believe you. :)  This is clearly not my area.

> So this does not seem to explain why ahci(4) fails to attach to your
> SATA controller.  I suspect that your bios or motherboard fails to use
> AHCI mode.  Maybe there is a later bios revision,

There is no later BIOS available, at least not from Dell. This is a
Latitude D620 laptop. And as I said previously, there are no BIOS
options that mention anything even remotely similar. There are two
hard drive related options. One is related to making it "slower and
quieter" vs. "faster and noisier." Guess which one I picked. :)  The
other is related to power management (DPMI).

I did look up the spec sheet on the hard drive last night, and
although it does mention SATA and NCQ it does not explicitly mention
if you're interested.

I also didn't see any mentions of jumpers on the drive to enable AHCI,
which I was kind of hoping for since that's pretty easy to remove.

> or some jumper
> settings on the board that will allow it to be enabled.  You may have
> to talk to the manufacturer. 

I would be willing to dive into that if someone could give me clear
guidance that one exists. I'm not really eager to open the
case otherwise.

> Of course, there is a small chance that
> there is a problem with our drivers.  Have you tried a live CD of a
> Linux distro, to see AHCI works with another OS?

No, but I'm happy to do so. Any suggestions on what distro is most
likely to succeed, and what to look for? I have used Ubuntu for a
project in the past with good success but I'd be willing to try
anything that folks think will work.

In any case I do appreciate your time on this. I run -current on
purpose to try out new features, help get them fleshed out from a
"regular user" perspective, and to expose bugs (often my own of
course). Better performance and cool new toys don't hurt either ...



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