Re: [pci] ucf file

[jazimme2@yahoo.com]

This is veering offtopic, but I think a correction is in order because the I 
don't think the original poster was cc'd on the response:

Foot in mouth.  That's what comes from giving a pat answer like I did, 
not having time to think it over.  Sorry.  Read on...

---------------
>From Mike Dini:
All of our stuff does this.  You only need two layers to do PCI with a 
1mm BGA.  You generally need a 4 4 trace width board.
Also, the app note, 157, isn't entirely correct.  It is not as aggressive as 
possible.
---------------

While I agree in theory, my response to this would be 4/4 boards are 
more expensive, and a good many prototype places I've seen do not 
support less than 5/5 (Advanced Circuits for one).  Of course, you could 
always pay a little more, get more boards, and go to production-level 
specs.  Also, Mike, when you say two layers, do you mean two *signal* 
layers?  That would be a 4-layer board counting power and ground 
planes.  So I guess my answer would be yes, you could do it with two 
signal layers if either you leave some pins unconnected or use a finer 
geometry.
j.
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