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Date:      Fri, 25 Oct 2002 09:47:51 -0700 (PDT)
From:      Linh Pham <lplist@closedsrc.org>
To:        Kevin Stevens <Kevin_Stevens@pursued-with.net>
Cc:        "Jack L. Stone" <jackstone@sage-one.net>, lewiz <purple@lewiz.info>, Steve Warwick <ukla@attbi.com>, <freebsd-questions@FreeBSD.ORG>
Subject:   Re: UDMA limited to 33 - resolution
Message-ID:  <20021025094521.B58366-100000@q.closedsrc.org>
In-Reply-To: <20021023161917.H11289-100000@babelfish.pursued-with.net>

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On 2002-10-23, Kevin Stevens scribbled:

# However, it *is* correct that all devices on a UDMA channel must support
# UDMA, so yes, the above is a problem.  I don't recall if all devices must
# also be the same UDMA speed (66/100/133) or not, bbelieve that is true
# too.  This is not a BSD issue, it is part of the UDMA spec.

IIRC-

The channel will run at the speed of the slowest device, meaning that if
you have a drive that is capable of ATA/66 and a drive capable of ATA/33
on the same channel, then the channel will run at ATA/33.

If you have a drive at ATA/100 and a drive that is only capable of PIO4,
then the speed of the channel will be knocked down to either PIO4 or
ATA/33 (the latter will only occur if the PIO4 drive is also capable to
running at ATA/33, just without DMA).

-- 

Linh Pham                                         lplist@closedsrc.org
Webmaster and FreeBSD Geek                        http://closedsrc.org
closedsrc.org                       Every solution breeds new problems


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