4.2bsd uba question (too many zero vectors)

[Alan Parker]

I'm trying to add another dhdm (Able) to my /780 4.2 system.  At
the same time, I'm removing a dmf-32 (also Able).  This is my uba
startup before:

dh0 at uba0 csr 160040 vec 200, ipl 15
dm0 at uba0 csr 170510 vec 100, ipl 14
dh1 at uba0 csr 160020 vec 210, ipl 15
dm1 at uba0 csr 170500 vec 104, ipl 14
dh2 at uba0 csr 160320 vec 340, ipl 15
dm2 at uba0 csr 171000 vec 410, ipl 14
dh3 at uba0 csr 160340 vec 360, ipl 15
dm3 at uba0 csr 171020 vec 430, ipl 14
dz0 at uba0 csr 160100 vec 300, ipl 15
dz1 at uba0 csr 160110 vec 310, ipl 15
dz2 at uba0 csr 160120 vec 320, ipl 15
dz3 at uba0 csr 160130 vec 330, ipl 15
dmf0 at uba0 csr 160400 vec 764, ipl 15
acc0 at uba0 csr 167600 vec 270, ipl 15
ec0 at uba0 csr 164324 vec 440, ipl 16

This is when I replace the dmf with the dhdm (of course, this
kernel is configured for the dhdm instead of the dmf):

dh0 at uba0 csr 160040 vec 200, ipl 15
dm0 at uba0 csr 170510 vec 100, ipl 14
dh1 at uba0 csr 160020 vec 210, ipl 15
dm1 at uba0 csr 170500 vec 104, ipl 14
dh2 at uba0 csr 160320 vec 340, ipl 15
dm2 at uba0 csr 171000 vec 410, ipl 14
dh3 at uba0 csr 160340 vec 360, ipl 15
dm3 at uba0 csr 171020 vec 430, ipl 14
dh4 at uba0 csr 160400 vec 240, ipl 15
dm4 at uba0 csr 171040 vec 120, ipl 14
dz0 at uba0 csr 160100 vec 300, ipl 15
dz1 at uba0 csr 160110 vec 310, ipl 15
dz2 at uba0 csr 160120 vec 320, ipl 15
dz3 at uba0 csr 160130 vec 330, ipl 15
acc0 at uba0 csr 167600 vec 270, ipl 15
uba0: too many zero vectors
uba0: reset dz0 dz1 dz2 dz3 acc0
ec0 at uba0 csr 164324 didn't interrupt

What does the too many zero vectors message mean? The problem
seems to be related to the 3Com board (ec0) because with it out
of the configuration, the new dhdm works just fine.  I tried
moving ec0 to the top of the uba configuration, but it also fails
there.  Notice that the vectors of the new dhdm are far away from
the ec0 vector (440).  Any ideas would be appreciated.