Very high system %cpu on 4.3beta VAX

[jbs at mit-eddie.UUCP]

I'm running 4.3beta on a VAX-11/750 with one dz, two Eagles on an
Emulex SC750, a TU78 on an MBA, 4MBytes of memory, and some ethernet
board.

I see very high system cpu% (30-70) when running "vmstat 5" (or top)
often (but not always) both when the system is busy, and when it is
relatively idle.

Although vmstat reports an interrupt rate of 40-50 or less, vmstat -i
shows lots of dzx0 interrupts occuring (i.e. I run it twice and
compare the totals) and it reports an averate rate of 77.

We don't use the dz's for very much, just a few dialups, which are
used mostly for uucp (a post-4.3-release from Rick Adams).  

The ethernet doesn't see very many packets (<10/sec usually)

My question is: Is something wrong, or is this much
system cpu% to be expected?  Is there anything I can do to reduce it?
Would replacing the dz help?  If so, with what?  Is there some
configuration parameter that might be wrong?

Jeff Siegal