Jeff,
You bring up a good point in the fact that I believe your refering to
detecting 80 wire vs. 40 wire. We've not tried to use this to our
advantage, but it could have some merrit. What does the driver do if it
encounters a 40 wire cable and the drive says it's capable of DMA5?
Best wishes,
John
From: Jeff Garzik <jeff@xxxxxxxxxx>
To: John Treubig <jtreubig@xxxxxxxxxxx>
CC: linux-scsi@xxxxxxxxxxxxxxx, linux-ide@xxxxxxxxxxxxxxx
Subject: Re: Controlling PATA access speeds
Date: Thu, 1 Jun 2006 14:52:44 -0400
On Thu, Jun 01, 2006 at 12:25:45PM -0500, John Treubig wrote:
> We are currently using Promise Ultra133 TX2 (PDC20269 chip; pata_pdc2027x
> driver, kernel version 2.6.15) to test and access PATA drives. If my
> understanding is correct, during boot, a drive is queryied to determine
> it's maximum access speed and the driver sets the access speed to be no
> higher than the drive can handle. This is not speed testing the drive,
but
> just the drive firmware reporting it's maximum designed transfer rate.
Due
> to design constraints of the cabling to the drives, we need to force the
> access speed lower than what the Drive reponds. Is there a mechanism to
> tell the driver/LibATA to set the access speed to go no higher than a
value
> I supply? This can be a static setting that is set at boot, as it does
not
> need to be a dynamic setting.
The driver includes code to do cable detect. Is this insufficient for
some reason?
Jeff
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