gEDA-user: six-layer stack

[Larry Doolittle <ldoolitt@xxxxxxxxxxxxxxx>]

Friends -

I'm "nearly done" with a six-layer design using pcb.  I have assumed
all along that the layers come in triplets, so with two ground planes
every trace is close to ground.  Nominal dielectric thicknesses would
be 5+5+30+5+5 mils.

Following this group's lead, I have investigated Advanced Circuits as
a possible board fabricator.  While they say they can do almost anything
in production, their prototype service has only a few six-layer stackups
available, none of which come close to my concept.
   http://www.4pcb.com/service_circuit_boards_online_instant_dieletric_stackup_6layer.htm
What they do have is a 0.045 laminated thickness board with three
doublets.  Approximate dielectric thicknesses are 4+14+4+14+4 mils.

With some effort, I could adapt my layout to this stack.  It would
mean squeezing down my use of the one inner routing layer, and
turning most of it into a ground plane.  That way the inner power
plane has an adjacent ground to form the other half of a capacitor.

My question to this group (thanks for your patience) is whether this
Adv.Cir. six-layer stack is typical for the industry?  Or are there
just as many companies out there for whom my original concept is
standard?  I think I read that commodity motherboards have recently
moved from four layers to six.  What's their typical stackup?

      - Larry