Date: Mon, 27 Jun 2011 00:10:51 -0700 From: perryh@pluto.rain.com To: freebsd-hardware@freebsd.org Subject: UDMA cables vs speeds Message-ID: <4e082cfb.RsTdPgXYWUCS9sX7%perryh@pluto.rain.com>
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Should an 80-wire Ultra-ATA data cable intended for use at UDMA66 or UDMA100 also work at UDMA133, or does the higher speed require different cabling? Background: I've been experiencing occasional UDMA ICRC errors on the IDE port of a PCI SATA/IDE controller card using the VIA VT6421 chipset, and I've noticed that "atacontrol mode" reports the port speed as UDMA133. The data cable is brand new, but it came with a UDMA100 card. (I got much worse results with a different 80-pin cable, which looked similar but may have been intended only for UDMA66.) I've found several similar reports in the forum and mailing-list archives, with no definitive solution but quite a few "it works for me" responses, and one observation that the VT6421 seems to work well with some drives and not so well with others. It occurs to me that the difference might, perhaps, involve the DMA speeds (which aren't mentioned).
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