Date: Wed, 17 Sep 1997 08:34:33 -0700 From: desmond@ic.eecs.berkeley.edu To: "Taras M. Dowhaluk" <tarasd@visiondb.com.au> Cc: aic7xxx@freebsd.org Subject: Re: AHA-2940 Ultra/Ultra Wide Message-ID: <199709171534.IAA30585@bips.EECS.Berkeley.EDU> In-Reply-To: Your message of "Mon, 15 Sep 1997 22:00:29 %2B1000." <m0xAZnh-003pfsC@kyoko.mpx.com.au>
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Taras M. Dowhaluk wrote: > Dan Eischen wrote: > > > > I'd also suggest using one of your disk drives to terminate the bus, > > and not your JAZ. Perhaps someone else can comment on whether your > > QUANTUM FIREBALL ST6.4S 0F04 needs firmware upgrades? Are you uising > > tagged queueing? > At the moment I have: > 2940 - disk 0 - disk 1 - Jaz. > Someone suggested that I turn the disk drives upside down such that > pin 1 faces the other way, that way I can run my scsi cable so that I > have 2940 - Jaz - disk 1 - disk 0, if you know what I mean. I had horrible problems using a ZIP in my external SCSI chain. I have always used an active terminator, but the ZIP (as does the Jaz) uses SCSI-1 cabling, and this seems to be the source of many problems, even when transfers do not involve the ZIP. I am using the stock 2.0.30 kernel. Putting the ZIP at the end (even with an active terminator) does not seem to terminate the bus properly -- I witnessed retries accessing other devices. Putting the ZIP in the middle seems to eliminate the retries because at least the end device is next to an active terminator. However, I found a more sensitive test: whether my DAT streams properly. It will only stream properly when I completely remove the ZIP from the chain. I am not confident I am ever getting proper termination with the ZIP involved because of the silly SCSI1 cable. Another sign of this is that the auto-termination feature of the 2940 seems to be confused (it fully terminates) whenever the ZIP (and its SCSI1 cable) are attached. My setup is: internal internal ultra-wide --- ultra -- cd -- 2940UW -- ZIP -- DAT -- active disk disk term Internally, the narrow devices are on narrow->wide adaptors. Externally, cabling is a mess: SCSI-III --> Centronics and then for ZIP, Centronics to their funky SCSI1, back out to Centronics, with the remainder Centronics-style connectors and active terminator. But the total length is under 3 meters. This setup is stable (no retries appear in the logs), but tape backups get corrupted (the DAT does not stream and you can hear it seeking a lot). For backups I therefore run: internal internal ultra-wide --- ultra -- cd -- 2940UW ---- DAT -- active disk disk term I have concluded that while you may get no SCSI errors, the ZIP messes up termination enough that it isn't worth having on the external chain (I wish I got an IDE internal ZIP). I don't think the Jaz is any different in cabling or termination. Desmond Kirkpatrick
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