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Re: Large 50-Pin SCSI Drives

On Sat, 16 Oct 2004 13:45:12 -0400, Chris Zakelj <c_(_dot_)_zakelj_(_at_)_ieee_(_dot_)_org>

>J.C. Roberts wrote:
>>I'm patient and I try to do my planing in advance rather than post
>>mortem. Last year when the call for 50-pin hardware went out to this
>>list, I thought the same thing as everyone else when I saw how expensive
>>the 18GB drives were then (18GB $175usd) -I thought "it no big deal
>>since it's old tech, nobody will want it and the price will eventually
>>drop to the floor over time." I was wrong and the problem has gotten
>Just an off-the-cuff pair of questions.... First, if the demand is still 
>so high (and apparently getting higher), why hasn't a manufacturer 
>noticed and spun up their 50-pin lines again?  This looks to have great 
>profit potential... the research/design/QA was done years ago, 
>manufacturing techniques have improved, and there's a market sitting 
>there waiting to be served.  Having done DMS (obsolete) part support 
>with Northrop-Grumman, I can't believe there isn't a supply of the chips 
>used on those boards somewhere as well.  

The lack of a supplier for drives of this type has me a bit surprised as
well but not too much. I know NASA is still using paper tape storage for
some systems. Since you've done the DMS/obsolete thing, you know why
they do it but most people don't realize all the details involved. For
those following the tread, I'll explain it.

Basically, once a system is "certified" to do a particular task, they
maintain it. There are two costs involved. The cost of testing something
so they can certify it works for a task and then there's the costs paid
over years/decades of finding all the things that can/will go wrong and
how to deal with them. In the NASA paper tape storage example, NASA
knows the bugs and how to deal with them if they occur, so they can
count on the system to work "as expected" without any unforseen
problems. When the life of an astronaut is on the line, that knowledge
is absolutely priceless. NASA has a quota of spares parts sitting around
waiting for something to fail, so they can fix anything that goes wrong
and I'm sure some of those spare parts had to be custom built at
significant expense because they are simply no longer available on the
open market.

I've been told every space shuttle mission to this very day in some way
counts on those old paper tape systems. Considering the price and size
of the average hard drive these days, the fact such systems are still in
use is kind of mind blowing.

The 50-pin scsi disks will eventually take the same route as the paper
tape storage systems; they will no longer be available on the market and
will need to be custom built at great expense to maintain parts quotas
for certified systems.

>Second... I've tried to grok 
>the pages I've found on Google, but none of them explain why these 
>68->50 pin converters screw things up.  Anybody mind educating me?

Marco or possibly Theo are the best people to answer this question. I
don't know the exact details of the problem or the affected
systems/interfaces. I'm still trying to find out the latter.


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