Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!sjsca4!poffen
From: poffen@sj.ate.slb.com (Russ Poffenberger)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Layered M/B?
Message-ID: <1990Jun5.145831.26729@sj.ate.slb.com>
Date: 5 Jun 90 14:58:31 GMT
References: <6811@ucrmath.ucr.edu> <838@peyote.cactus.org>
Reply-To: poffen@sj.ate.slb.com (Russ Poffenberger)
Organization: Schlumberger Technologies, San Jose, CA.
Lines: 29

In article <838@peyote.cactus.org> woan@peyote.cactus.org (Ronald S. Woan) writes:
>In article <6811@ucrmath.ucr.edu>, lulu@ucrmath.ucr.edu (david lu) writes:
>> What exactly does it mean for a motherboard to be "layered"?
>> I've heard of "4-layered motherboards", so I assume that there
>> are other n-layered m/b's as well.  Are all m/b's layered?
>
>Layered is just what it implies, several layers of 'glass sandwhiched 
>together to allow more conductor paths in a smaller amount of space.
>Most motherboards are indeed 3+ layered these days. Personally I have always
>felt that this is not always a good thing as you have to be aware of possible
>interference and capacitance effects.
>

Because layered boards are more complex to manufacture, and defects potentially
difficult to fix, having a board with a lot of trace layers is not necessarily
the best. Usually you want a 4-layer board because this implies that power
and ground are run on separate layers and are usually preferable for
maintaining signal integrity on the other two (signal) layers by acting like
shields. If you had a choice between a 4 layer and 6 layer board, both of equal
functionality, take the 4 layer board. This usually implies that the designer
of the board took a little more effort is laying out the board, rather than
resorting to more layers to route all the traces, not to mrntion that the 4
layer board would probably be a little cheaper and more reliable.


Russ Poffenberger               DOMAIN: poffen@sj.ate.slb.com
Schlumberger Technologies       UUCP:   {uunet,decwrl,amdahl}!sjsca4!poffen
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