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From: jay@metran.UUCP (Jay Ts)
Newsgroups: comp.unix.sysv386
Subject: Re: Need Recommendations On 386/486 UNIX systems
Summary: about redundancy
Keywords: unix, 386/486
Message-ID: <358@metran.UUCP>
Date: 23 Dec 90 03:09:46 GMT
References: <8204@uwm.edu> <1990Dec18.002013.28881@news.iastate.edu> <1990Dec22.143706.4493@virtech.uucp>
Organization: Metran Technology, Tampa, Florida
Lines: 47

In article <1990Dec22.143706.4493@virtech.uucp>, cpcahil@virtech.uucp (Conor P. Cahill) writes:
> In article <2710@sixhub.UUCP> davidsen@sixhub.UUCP (bill davidsen) writes:
> 
> >|     4. 16 port serial card?
> >
> >  Two 8's. You might find performance a hair better one way or the
> >other, but redundancy says use two, and there's no drawback I can see.
> >*Smart* cards, please.
> 
> I would recommend a single card.  (Slots are precious commodities, don't
> waste them).  The card I like best (and of course this is just personal
> opinion) is the Megaport-24.

One of my clients suffered a direct lightning strike to their building this
summer.  The computer manager watched the electricity arc across the ceiling.
The only thing that kept them from being able to do useful work with their
computer afterwards was a blown multiport I/O card.  When the mp card was
removed from their system, it booted and ran workably, but of course all of
their terminals were useless.  I think this sort of situation is what Bill
is referring to when he says "redundancy says use two".

It's a limitation, of course, if you don't have enough slots, and it's
probably more expensive, too.  Also, if a 2-card system were hit by lightning,
maybe both would fail.  Which bridges nicely into my main point.

Arnet reports that 70% of their cards were returned due to surges on the
serial lines.  Upon inspection, the card referred to above had a (physically)
blown line driver chip.  Later, we found that a few of the Wyse 60 terminals
had the same problem (they use the same industry standard chips).

I read recently (in an electronics industry mag, I think; sorry I don't have
a definitive reference) that even if you have a UPS on the computer, and
every terminal and other peripheral has a surge protector, not only is the
system still vulnerable to this problem, it is MORE vulnerable!  Problem is,
the MOV surge protectors shunt the electrical surge to ground, which sets
up massively different electrical ground voltage potentials between equipment
plugged in at different places in the building's wiring.  Say, in different
rooms.  The result of this is that a surge is created in the serial line,
which suddenly becomes the electrical connection between equipment running
off grounds that are several thousand volts apart.

So here's my recommendation:  Arnet now includes port surge protection as
standard equipment in their multiport cards.  Try the Smartport-16s.

				Jay Ts, Director
				Metran Technology
				uunet!pdn!tscs!metran!jay