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LSI chips & local bus

To: riscy@pyramid.com
Subject: LSI chips & local bus
From: adyer@zarniwoop (Andrew Dyer)
Date: Mon, 5 Jul 93 10:25 PDT
In-reply-to: Jerry Callen's message of Tue, 6 Jul 93 13:47:20 EDT <9307061747.AA04298@luna.think.com>
Reply-to: riscy@pyramid.com
Sender: riscy-request@pyramid.com
Large PLCC sockets usually have reliability problems with time. PLCC
sockets rely on tension to keep the contacts together.  If they fail
the sockets usually break in the corner and some tension is lost -
with heat stress the contact will open and close.  Very annoying to debug.
PGA sockets are better bcause they have machined pins which make better
contact, and do not rely on tension to make contact.  Yes they are hard
to remove - they're supposed to be.  If you have the correct tool, it is not 
so difficult.  If we make a board with PLCC sockets, make it SMT sockets,
so I can pull it off and SOLDER my CPU to the board!

The LSI logic 33000 and 33050 are pin compatible as far as I know.

Also RE: local busses - I say for expansion that we should bring all
of the CPU local bus signal to a connector(s) and make sure that the
drivers on the PCB are tri-state or open collector.  That way for
minimal cost those of us who want to play with fast CPU interfaces
can.  You don't even have to stuff these extras - we who can design
such a thing can probably solder.


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