Changes between Version 1 and Version 2 of Ticket #228, comment 2


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Timestamp:
06/22/2021 01:03:33 PM (5 years ago)
Author:
Gary Dixon

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  • Ticket #228, comment 2

    v1 v2  
    5353
    5454
    55 Machine conditions stored at that location for the fault show contents of A and Q registers,
    56 as well as other regs used in code just before the fault.
     55Machine conditions stored at that location for the fault show contents of
     56A and Q registers, as well as other regs used in code just before the fault.
    5757
    5858azm:  mc pds$signal_data -long
    … …  
    115115
    116116Source shows Q being added to bb|governing_credit_bank (tc_data|451)
    117 which is a positive integer after the ASQ instruction ran.  But it is difficult to determine
    118 its value before that addition occurred.  I suspect it was a negative value.
     117which is a positive integer after the ASQ instruction ran.  But it is difficult
     118to determine its value before that addition occurred.  I suspect it was a
     119negative value.
    119120
    120121azm:  d pr3|451 -octal
    … …  
    123124   451      0 122615176160
    124125
    125 However, the asq instruction (which was executing when the overflow fault occurred)
    126 is performing signed arithmetic.  Since the sign-bit is ON in the Q register,
    127 a large negative quantity is being added to a smaller positive value.
     126However, the asq instruction (which was executing when the Overflow Fault
     127occurred) is performing signed arithmetic.  Since the sign-bit is ON in the
     128Q register, a large negative quantity is being added to a smaller positive value.
    128129The result should be a negative value.  An Overflow fault is triggered because
    129130the Overflow Mask indicator (oflm) is NOT set in the Indicators recorded