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From: hogan@rosevax.UUCP (Andy Hogan)
Newsgroups: net.micro.mac
Subject: Re: Re: RAM ugrades (sockets)
Message-ID: <234@rosevax.UUCP>
Date: Wed, 6-Nov-85 18:17:07 EST
Article-I.D.: rosevax.234
Posted: Wed Nov  6 18:17:07 1985
Date-Received: Sun, 10-Nov-85 09:37:09 EST
References: <1058@decwrl.UUCP> <372@gcc-milo.ARPA>
Organization: Rosemount Inc., Eden Prairie, MN
Lines: 40

>In reference to the reliability of sockets:
>I seem to recall the rule of thumb being:
>The addition of a socketed chip, in place of a soldered chip has the
>same effect upon reliability as adding another chip.  I believe this comes
>from an ATT manual on reliability.
>
>Thus, if Apple (for example) was to add socketed RAMs, it would be 
>equivalent, in terms of reliability, to adding 16 more chips to the
>digital board.  All in all, I'll take the soldered version.
>
>				Tim Peacock

Hmm.  This seems like an old rule, but is probably still good if you substitute
"another small- to medium-scale integrated TTL chip" for "another chip". Newer
technologies and larger scales of integration have greatly decreased the 
reliability of chips vs. sockets.  Socket manufacturers have not stood still
either (they know that they get bad press on reliability) so they have 
increased socket reliability.

Socket reliability is only one factor.  When production quantities are in
the region that Apple works in, the cost of the sockets (and installing them,
etc.) becomes far greater than the cost savings in repair and other cost 
advantages of socketing.  So there is enormous pressure on a large manufacturer 
not to use sockets.  From Apple's point of view, they are a burden.  From MY 
point of view, they were necessary when I did the Dr. Dobbs upgrade, because 
they allow me to replace dead chips easily and (potentially) allow me to add 
in 1 Meg chips when they are available (with some more hacking and new Apple
ROMs which I optimistically assume I can get (1/2 :-) ).  I also got very 
good sockets at an enormously low cost....

In any case, sockets for ICs (particularly memory and other expensive ones)
are something that should be designed in until a total cost analysis pushes
them out.  When that happens, the manufacturer should be aware that he is
trading cost against problems that are very tough to measure, such as 
customer satisfaction, and weigh that in the decision also.

-- 
Andy Hogan   Rosemount, Inc.   Mpls MN
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