pre15 woes w. both 68pin & 50pin

[Smith, Jeremy]

You mention a SCSI-II external tape drive. I'll assume that it uses a 50-pin
connector of some sort. If that's the case and you end the bus with a 25-pin
Zip drive doesn't that leave your bus with a possible 25-pins that are
essentially just hanging off the bus w/o termination? I tried to arrange a
bus in a similar manner once and I continually got bus resets. Removing the
Zip and connecting it to an AHA-1515 did the trick. 

Just a thought.
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Jeremy Smith
System Administrator
Bell+Howell MPS
smithj at mps.bellhowell.com <mailto:smithj at mps.bellhowell.com>

1400856 at mcipage.com <mailto:1400856 at mcipage.com> 
Day: (919)767-6530
Eve: (919)859-5690
"Truth in philosophy means that concept and external reality correspond."
George Hegel (1770-1831)
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		-----Original Message-----
		From:	Doug Ledford [mailto:dledford at dialnet.net]
		Sent:	Wednesday, October 07, 1998 4:16 AM
		To:	Karl O. Pinc
		Cc:	aic7xxx at FreeBSD.ORG
		Subject:	Re: pre15 woes w. both 68pin & 50pin

		Karl O. Pinc wrote:
		> 
		> 2.0.35 kernel w. pre-15 patch (& redhat patches)
		> Micronics W6LI motherboard w. built in aic7880u & adaptec
bios 1.24
		> (dual PPro, but running w/o SMP -- which I suspect fails)
		> 4 Seagate ST-15230W hard drives (68 pin)
		> (and, in the following physical order)
		> Yahama 4260t series CDRW (50 pin), internal
		> Python Dat tape drive (scsi II), external
		> HP scanner detected as a C2520A (w. 1 centronics & 1 ugly
25pin D connector)
		> Epson zip drive, external (Iomega licensed knock off w.
25pin D
		> connectors & internal termination on)
		> 
		OK...a few suggestions.  Yes, you probably are trying to
slide too much
		stuff onto one bus.  Personally, I like the 2910C cards for
something cheap
		to separate things up and that also works fine with external
stuff.  Second,
		the errors you note indicate that there may already be bad
data written to
		the disks as a result of all of this.  A SCSI bus will catch
single bit
		parity errors and pass 2 bit errors without any notice of
problem.  From
		what I see, you may be susceptible to the dual bit error
problem.  There is
		simply too much going wrong on your bus to trust that all
errors will get
		caught by parity.  I would see about getting a custom made
internal wide
		cable for the drives that only leaves about 3 to 4 inches
between each wide
		drive, terminate the last wide drive of course, hook the
other end to the
		controller and terminate the controller.  Then, don't hook
any narrow
		devices to that controller.  I would use something like the
2910C for all
		narrow devices be they internal or external (this assumes
none of the
		internal stuff is Ultra, if it is, then you would need
something like a
		2940AU instead).

		-- 

		 Doug Ledford  <dledford at dialnet.net>
		  Opinions expressed are my own, but
		     they should be everybody's.

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