problem with ux400

[Moon@STONY-BROOK.SCRC.Symbolics.COM (David A. Moon)]

    Date: Tue, 26 Jun 90 15:05:33 -0400
    From: steven@linc.cis.upenn.edu
    
    We've been having a problem with our ux400.
    Every so often, it pops into the cold load stream with the following error:
    
    --> Error in the dispatcher, using the cold load stream <--
    
    Trap: The second argument to the %32-BIT-DIFFERENCE instruction, #<DTP-PACKED-I
    NSTRUCTION- 77 37777777777>, was not a fixnum
    
    PROCESS::UDPATE-PROCESS-METERS

    Any ideas?

I suspect that if you do the following:

(compile (defun tst () (loop while (typep (sys:%microsecond-clock) 'fixnum))))
(tst)

it will not run for very long.  It should run forever of course.
Call field service and have them repair the microsecond clock on your
UX400 processor board, which is sometimes returning all 1's, including
the tag bits, instead of the correct clock reading, and keep repairing
it until the above test case passes.