system crashes trap type 8

[Tom Bradshaw]

system crashes with an error message ...

trap type 8, code=8c20004, pc=800137c6

The pc always points to the dzxint routine. The parameter passed
to the dzxint routine, at the time of the crash, has the wrong value.
Therefore this parameter, which is a pointer into the tty structure
is pointing to invalid information causing the system to crash.
This can happen twice a day, generally during peak times.

questions are ...
1) In the trap message what does "code=8c20004" mean.
2) If anyone has experienced similar problems please reply any
   helpful information.

hardware ... VAX 11/780 with 5 dz11
		             1 dup11
			     2 dr11c
			     1 uda50
			     1 interlan ethernet board
			     1 smv15 controller for ampex drives
			     1 optronics scanner
	     running UNIX 4.1 BSD