Date: Wed, 06 Jul 2011 21:35:22 -0700 From: perryh@pluto.rain.com To: freebsd-hardware@freebsd.org Subject: VIA VT6421 w/a (Re: UDMA cables vs speeds) Message-ID: <4e15378a.FzdckfPKoy0B4rU6%perryh@pluto.rain.com> In-Reply-To: <4e082cfb.RsTdPgXYWUCS9sX7%perryh@pluto.rain.com> References: <4e082cfb.RsTdPgXYWUCS9sX7%perryh@pluto.rain.com>
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This is for the archives. The original posting is here: http://lists.freebsd.org/pipermail/freebsd-hardware/2011-June/006704.html > 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? Answer: as nearly as I've been able to determine, there are only two kinds of PATA data cables: the original 40-wire variety that work for PIO and for UDMA33, and the newer 80-wire variety that should work for all modes. > ... 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 ... > 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 DMA speed definitely seems to be a factor. The errors seem to have been completely eliminated after I used atacontrol mode ad8 UDMA100 to limit the maximum transfer rate. Throttling the DMA speed is not an ideal solution, and I still have no clue _why_ it doesn't work reliably at UDMA133, but this does seem to have gotten around the problem.
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