We also suspect Protel is at fault for the 28 mil holes.  I think it is a default in 
Protel setup.  
As far as High Speed design rules,  You will need to stick with spectra for now, since 
Electra does not support differential pairs of matched lengths.  I did not try blind 
and buried vias, but I did use prerouted "via in pad".  Electra was cleaner since it 
let these connections alone and I did not have to create any "forget" commands. 
We also tested the "BUS" command on both routers. The test board was a simple 
backplane with identical connectors on same Grid. Spectra was slightly better however, 
 neither Electra or Spectra routing would be acceptable with this command.  
One thing we did notice....since both routers use a "manhattan" topology to place 
traces,  On large busses, Electra has  very few loops.  It sticks to the floorplan 
very well.  I have a tendency to use the "limit way" command on most of my designs.  
This forces the router to lay traces parrallel to each other on the same layer. This 
increases the density of the routing.  Limit way is a little tighter on Spectra.  I 
ran tests on both routers, using limit way then ran test without limit way.  In both 
cases, Electra managed 500-700 less vias out of 7800. 

What I was most impressed with was that it left the locked preroutes tollally alone. 
Honestly, this is the first router that this worked with.   If  you think Spectra is 
leaving them alone, look closly at your design.  On some occasions it place traces 
either over or around your preroutes.  The only way to avoid this is to create 
"forget" classes.
Here is the way the classes and DSN file works in Protel.   Protel does not export 
classes. I wish it would.  If you want to create widths lets say for DATA D0-D7, 
created a classs called DAT0_7, then create and invidual width rule for that class.  
When Protel exports the DSN file , it will assign an INDIVIDUAL rule to the nets in 
the class.  The same applies to via  type, toplogy, max via, and clearance. Protel 
extracts the class and breaks it down to net.  That is perfectly fine ...perhaps 
cumbersome but it works.  You still may want to look at this router.  ELecta is 
working on adding High Speed rules

Mike Reagan
Frederick MD

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