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Path: utzoo!utgpu!watserv1!watmath!uunet!shelby!apple!portal!cup.portal.com!thad
From: thad@cup.portal.com (Thad P Floryan)
Newsgroups: unix-pc.general,comp.sys.att
Subject: Re: Hard disk woes..
Message-ID: <31910@cup.portal.com>
Date: 20 Jul 90 05:05:37 GMT
References: <2069@lakesys.lakesys.com> <31882@cup.portal.com>
Organization: The Portal System (TM)
Lines: 47

chad@cup.portal.com (Chad The-Walrus Netzer) in <31882@cup.portal.com> writes:

	I have this same problem (ie. WD2010 chip doesn't work) and I'm also
	using the Microbotics 3085, but I have a 2010(B) chip (Not A).  I've
	tried it with two different "B" chips, but neither worked correctly.
	I thought it may be due to a motherboard incompatibility (I have a
	Rev. B board) but Thad Floryan has said that he has a 3085 running
	perfectly with a Rev. B Motherboard using a WD2010B, so I am at a
	loss.  What motherboard revision do you have?  I want to test the chip
	and drive on my revision C motherboard to see if that has any effect,
	and I'll let you know what happens.

	Anybody else have any ideas or experiences with the WD2010 and/or the
	Microbotics 3085.  I'm particularly interested to know what
	motherboard revisions people have and haven't gotten it to work with.

``Microbotics''??  Wrong newsgroup! :-)  The drive in question is "Miniscribe."

But, seriously, there DO appear to be a number of systems that are unable to
function with the WD2010 and, since Chad lives near me and is working with me
at NIS this Summer, we WILL attempt to find and post the solution.

The "Fire and Water Damage Restoration Team" should have my office back in
shape by this weekend and I'll then be able to consult the ol' schematics.
There ARE some differences in the disk driver circuitry flanking the 26LS31
and 26LS32 chips (the RS-422 disk data driver and receiver chips) and perhaps
those differences source these problems; hopefully we'll know soon.

The UNIXPC breeds some s-t-r-a-n-g-e problems.  For example, a few weeks ago a
friend bemoaned his 3B1 reporting a "parity error" and going belly-up EVERY
time he requested a screen-dump-print or a long listing.  "Yeah, sure," I said,
"printer parity errors.  Uh huh." After thinking about it for a few minutes, I
consulted the schematics and instantly noticed that a spare buffer in the
74LS245 servicing the parallel port was ALSO used to coax the PERR* signal on
its merry motherboard meanderings.  Turns out that previously the printer cable
underwent the "joys" of live insertion (i.e. was plugged in with both the
printer and the system powered up) and a short ensued ... thus zapping the
74LS245 and the PERR* gate such that anytime the printer requested flow control
it would affect the PERR* buffer gate and halt the system.  Replacing the
74LS245 solved the problem.

There ARE enough differences between the various 3B1 motherboard revisions to
suggest possible interaction with a different disk controller chip.  Who knows,
perhaps the impedances of the WD2010 differ from the WD1010?  Chad and I will
be trying some things and will report the results.

Thad Floryan [ thad@cup.portal.com (OR) ..!sun!portal!cup.portal.com!thad ]