I'm seeing this on heavy IO on CS20(DS20L) running 3.0.1 MP kernel.  
Kernel drops to dbg with "panic: pmap_emulate_reference: !write but not FOR|FOE".

I've submitted a problem report: 
http://www.netbsd.org/cgi-bin/query-pr-single.pl?number=35284

Problem does not persist when running a single processor kernel.

I am not a developer, but I am willing to contribute whatever I can to facilitate work on this problem.  I have a few CS20s sitting idle that I would be willing to provide access to anyone willing and able to work on this.

Regards,
Brad Beck