Jami,

you missed a few important points.

Generating a netlist and loading it into your PCB is not hard to do. It is a
few more mouse clicks (maybe 20 seconds more work) than just hitting update.
Your time is surely not that valuable, is it??

like I said:
generate a netlist - it gives you the option to generate single pin nets if
you want - ie a net for every unconnected pin.
load the netlist into the PCB.

Now, if this is not the first iteration of the PCB (ie you havent just
placed all the parts on the board, its possible some preroutes will have
nets already assigned to them) And particularly if you have just changed
nets around on pins, as happens with FPGAs at layout time. you need to go to
the net manager in the PCB editor and unlock the primitives of the prerouted
BGA, then select all the primitives. Do a global edit on selected tracks,
and selected VIAS to set them all to "NO NET" Then lock them all again.

Then, you do that "update free primitives from component pads" thing. 

Now you won't have to make up any funny rules in your PCB, and you won't
have to sit there after a DRC working out what are valid shorted nets and
what aren't.

It's a pain, but the only way I know to update prerouted footprints
properly.

Using the "update PCB" menu item does not allow this, and so when you're
working with pre-routed BGA footprints, it is a better idea to work with
netlists, even if it isn't as immediately convenient.

-------------

As for my board (not that I need any more help on it, it's working great!

Its a 4 layer baord.
2 signal, 1 ground 1 power.
the power and ground planes have split planes on them.

Stackup is:
Signal
GND
PWR
Signal

All the high speed signals go on the top layer over the unbroken ground
plane. there is only one ground plane for the majority of the PCB, the other
grounds are around connectors where I have isolated grounds for different
I/O connections. 

The power plane IS split under the BGA because it requires 4 power rails. (3
actual power supplies, ome voltage reference for the gigabit transcievers) I
could possibly do a screen dump to illustrate this if you want but I guess
you know what they look like anyway.

What I was saying, is that for a design that requires only two routing
layers, a 6 layer board is slight overkill, no? one split power plane is
certianly usable if you are careful. Of course the usual caveats apply -
Your Mileage May Vary, Not Valid In All States,  For Internal Use Only, This
Is Not A Guarantee, etc etc etc, blah blah blah.



Julian

--
Julian Higginson - Design Engineer - Lake Technology.
Suite 502/55 Mountain St, Ultimo, NSW 2007, Australia.
Phone: +61 2 9213 9000 - Direct: +61 2 9213 9021
mailto:[EMAIL PROTECTED] - http://www.lake.com 
 



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