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Date: Thu, 02 Jan 2003 14:40:20 -0800
From: Ross Biro <rossb@google.com>
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To: Lionel Bouton <Lionel.Bouton@inet6.fr>
CC: Alan Cox <alan@lxorguk.ukuu.org.uk>, Andre Hedrick <andre@linux-ide.org>,
       Teodor Iacob <Teodor.Iacob@astral.kappa.ro>,
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Subject: Re: UDMA 133 on a 40 pin cable
References: <20030102182932.GA27340@linux.kappa.ro> <1041536269.24901.47.camel@irongate.swansea.linux.org.uk> <3E14B698.8030107@inet6.fr>
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>
> #1 How is the 40/80 pin detection done at the hardware level ?


On the motherboard end of the 80 conductor cable, the connector shorts 
one of the pins to ground (maybe pin 38).  The ide controller  just 
checks to see if the pin is pulled low or not.  Pulled low = 80 pin. 
 That's one of the reasons it's important to plug IDE cables in the 
correct way.

    Ross


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