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Date:      Tue, 12 Feb 2008 09:20:57 +0000
From:      Tom Evans <tevans.uk@googlemail.com>
To:        Dominic Fandrey <kamikaze@bsdforen.de>
Cc:        "Carlos A. M. dos Santos" <unixmania@gmail.com>, freebsd-stable@freebsd.org
Subject:   Re: RELENG_7: interrupt eating whole cpu core
Message-ID:  <1202808057.2126.45.camel@localhost>
In-Reply-To: <47ACA0E4.2030905@bsdforen.de>
References:  <47A9F835.1060200@bsdforen.de> <47AA0696.5020109@bsdforen.de> <7872AB6E-21DA-4E2D-93C0-D07CFA3A7E47@mac.com> <47AA0E3E.4020304@bsdforen.de> <e71790db0802071822l661bdcb8s6dfe5b94be11f0dc@mail.gmail.com> <47ABF66E.4040807@bsdforen.de> <e71790db0802080543g54d27bb8nfdc33e342f982b4@mail.gmail.com> <1202485501.2126.34.camel@localhost>  <47AC7FF6.1020801@bsdforen.de> <1202491071.2126.42.camel@localhost>  <47ACA0E4.2030905@bsdforen.de>

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On Fri, 2008-02-08 at 19:35 +0100, Dominic Fandrey wrote:
> Tom Evans wrote:
> > On Fri, 2008-02-08 at 17:14 +0100, Dominic Fandrey wrote:
> >> Tom Evans wrote:
> >>> If I try to turn on DMA, I just get WDMA2, which just doesn't cut it:
> >> I think any DMA mode is fast enough to handle a DVD drive. There's jus=
t no=20
> >> necessity for more.
> >>
> >=20
> > WDMA is not UDMA. Any UDMA variant would be enough. WDMA2 provides a
> > maximum of 16MiB/s, which will frequently lead to buffer underruns
> > viewing a DVD. UDMA2 provides a maximum of 33MiB/s, which IS plenty.
>=20
> 16MB/s is exactly what is needed for 12x DVD access. I think this is the =
usual=20
> speed for a Notebook drive nowadays and it suffices for me.
>=20
> >>>> # atacontrol mode acd0 udma5
> >>> current mode =3D WDMA2
> >> Same as for me. I'm satisfied with the speed of the drive.
> >=20
> > I'm rarely satisfied - I'm quite often not bothered enough to pursue :)
>=20
> Well, if 12x speed is not enough for you, you have to use an external dri=
ve.=20
> This is not a driver issue. It's just what your drive supports.

The chipset supports UDMA6, the drive supports UDMA6, I should be happy
with WDMA2 because 'thats what works'? Thanks for your 'help'. I'll
continue on here from myself.

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