Re: Playing with SATA NCQ

[Jeff Garzik <jgarzik@pobox.com>]

Erik Slagter wrote:
> On Sun, 2005-05-29 at 12:34 -0400, Jeff Garzik wrote:
>
> > > > Now, this patch is not complete. It should work and work well, but error
> > > > handling isn't really tested or finished yet (by any stretch of the
> > > > imagination). So don't use this on a production machine, it _should_ be
> > > > safe to use on your test boxes and for-fun workstations though (I run it
> > > > here...). I have tested on ich6 and ich7 generation ahci, and with
> > > > Maxtor and Seagate drives.
> > >
> > > Is this supposed to work on ICH7 in legacy mode as well?
> >
> > Nope.  ata_piix does not support NCQ (because the h/w doesn't support).
>
>
> If I understand this correctly: NCQ does not work on ICH7 in native mode
> (using ata_piix) because in this mode there is no NCQ available, right?

To be more specific, there are these modes:

	legacy mode		no NCQ
	combined mode		no NCQ
	native mode		no NCQ
	AHCI mode		NCQ


> > > Another question: is there a fundamental problem to have the ICH6/7
> > > enabled AHCI mode by the kernel instead of the BIOS? I know some BIOSes
> > > don't offer the choice to enable AHCI (like mine :-().
> >
> > Not a problem.  You just don't get to use AHCI and such.
>
>
> Huh?
>
> My question was if there is a fundamental reason why the AHCI mode of
> the ICH6/7 must be enabled by the BIOS, is there a reason why the kernel
> doesn't do it, or can't do it?

The BIOS sets up PCI resources necessary to use AHCI mode.

	Jeff


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