displaying useful output again:
db{0}> bt
cpu_Debugger(c1aa4800,c1aa8b1c,c1aa803c,1,c1aa48ec) at netbsd:cpu_Debugger+0x4
comintr(c1aa4800,cf38fc04,0,0,0) at netbsd:comintr+0x65c
DDB lost frame for netbsd:Xintr_ioapic_edge4+0xa8, trying 0xcf413ff4
Xintr_ioapic_edge4() at netbsd:Xintr_ioapic_edge4+0xa8
--- interrupt ---
--- switch to interrupt stack ---
cpu_idle(cf421e00,cf421e00,0,c0264950,cf421e00) at netbsd:cpu_idle+0x30
idle_loop(cf421e00,0,c01002d2,fbff,c01002d2) at netbsd:idle_loop+0x7a