Date: Tue, 15 Apr 2003 11:55:17 -0400 (EDT) From: Jameel Akari <jakari@bithose.com> To: "Kevin A. Pieckiel" <kpieckiel-freebsd-alpha@smartrafficenter.org> Cc: freebsd-alpha@freebsd.org Subject: Re: problem with UDMA mode on XP1000 Message-ID: <Pine.OSF.4.33.0304151146380.1028-100000@poptart.bithose.com> In-Reply-To: <20030415154229.GG90878@pacer.dmz.smartrafficenter.org>
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On Tue, 15 Apr 2003, Kevin A. Pieckiel wrote: > On Mon, Apr 14, 2003 at 09:22:00AM -0400, Andrew Gallatin wrote: > > > Rant aside, ATA cables are VERY sensative to EMI noise. What's > > happening to you is that the cable is either badly twisted, running > > Are these types of issues IDE specific, or are there similar issues with > SCSI cabling as well? Yes and no.. IDE's big failing (IMO) is that it's basically unterminated. It's tuned for a certain signal level and cable length in the hope that you don't need termination. There are a lot of variables, but in my experience IDE is more susceptable to radiated noise than SCSI cabling. I was always under the impression it was tuned for an 18" cable length but I'm seeing all sorts of sizes these days; I seriously doubt the 36"+ cables I see around are within spec. I've run max-length SCSI cables internally (with 5-6 attached devices) in a rather noisy system without any ill effect. OTOH, plain 40-pin IDE didn't fare well in that system.. CDROM was ok, hard disk was flaky. Switching to "UDMA" cables (80-conductor) resolved the issue, even though it wasn't a UDMA aware controller or drive in question. My Tivo used to randomly crash until I replaced its cheap 40-pin cable with a new UDMA one. Now it randomly crashes because I forgot to re-enable swap, but that's another matter... ;) I had the same sort of problem in an Alpha PC164, but in the end the onboard IDE was so terrible and Tru64 refused to run a hard disk on it, so I bought an ISP1040 and went SCSI, and it's been solid. -- #!/jameel/akari sleep 4800; make clean && make breakfast
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