 +_____________________________________________________________________
 ] AUTHOR:            ]                             ] DR:              ]
 ] HIRAM THOMPSON     ]    PASS PROGRAM NOTE        ]       37547      ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE: SEPT. 1987 ]
 ] LSIS/282-7225      ]      RELEASE NOTE( )        ] REV A: 09/11/95  ]
 ]____________________]_____________________________]__________________]
 ] OI/FLIGHT EFFECTIVITY:        ]  USER AFFECTED:                     ]
 ] REL 18 AND SUBS               ]  CREW ( )  GROUND (X)  DUMP ONLY ( )]
 ]_______________________________]_____________________________________]
 ]        MAJOR SOFTWARE AREA:       ] OPS MODES AFFECTED:             ]
 ]SSW (X)  GNC ( )  VU ( )  SM/PL ( )] 0, G1, G2, G3, G6, G8, G9, S2,  ]
 ]                                   ] S4, P9                          ]
 ]_____________________________________________________________________]
 ] SOFTWARE SUB-AREA: SPEC, UPLINK, TCS, SACS                          ]
 ]_____________________________________________________________________]
 ] PRINCIPAL FUNCTIONS: STCS, SULK, SS2                                ]
 ]_____________________________________________________________________]
 ] TITLE: RESTRICTIONS ON USE OF GPC MEMORY READ/WRITE CAPABILITIES    ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ]                                                                     ]
 ] GPC MAIN MEMORY CAN BE PATCHED IN REAL-TIME BY USING THE GPC MEMORY ]
 ] DISPLAY (G901 OPS DISPLAY AND SPEC 000), BY UPLINK, BY TCS AND BY   ]
 ] SACS.  USERS SHOULD BE AWARE OF THE FOLLOWING RESTRICTIONS          ]
 ] ASSOCIATED WITH THE PATCHING OF CODE OR DATA USING THESE            ]
 ] CAPABILITIES:                                                       ]
 ]                                                                     ]
 ] A. PATCHING SINGLE OR MULTIPLE 16-BIT HALFWORDS IN A SINGLE GPC, CS ]
 ]    OR AN RS, SHOULD BE AVOIDED IF THE CODE OR DATA BEING PATCHED IS ]
 ]    CONCURRENTLY BEING USED BY OTHER CPU OR IOP PROGRAMS. EXAMPLES   ]
 ]    OF POTENTIAL PROBLEMS INCLUDE:                                   ]
 ]                                                                     ]
 ]    -CYCLIC PROGRAMS MAY NEGATE OR MODIFY THE EFFECT OF A PATCH TO A ]
 ]     DATA AREA IN USE.                                               ]
 ]                                                                     ]
 ]    -IF THE PATCH IS TO AN I/O PROGRAM AREA OR BUFFER BEING          ]
 ]     REFERENCED OR MODIFIED BY THE IOP, THE RESULT COULD BE          ]
 ]     ERRONEOUS OR NON-HOMOGENEOUS INPUTS OR OUTPUTS.                 ]
 ]                                                                     ]
 ]    -IN A CS THE APPLICATION OF THE PATCH WILL NOT BE APPLIED AT THE ]
 ]     SAME POINT IN THE CS CODE EXECUTION IN ALL SET MEMBERS.         ]
 ]                                                                     ]
 ] B. CONCURRENT PATCHING OF MULTIPLE HALFWORDS (INCLUDES TWO 16-BIT   ]
 ]    HALVES OF A 32-BIT CODE/DATA WORD) VIA UPLINK, TCS OR SACS       ]
 ]    SHOULD ONLY BE PERFORMED WHEN THE "CONTIGUOUS" OPTION IS USED    ]
 ]                                                                     ]
 ]                 - CONTINUE ON SUPPLEMENT PAGE -                     ]
 ]_____________________________________________________________________]
 ]CONCURRENCE:                           ]APPROVAL:                    ]
 ]LSIS:   JEAN L. ZOPHY     DATE 10/18/95]                             ]
 ]     -------------------      ---------]                             ]
 ]ASD:   ERIC C. BINGHAM    DATE 10/19/95]                             ]
 ]     -------------------      ---------] DARRELL E. STAMPER 10/23/95 ]
 ]PF MGR: KAYLENE F. KINDT  DATE 10/20/95]------------------- -------- ]
 ]       -----------------      ---------] CHAIRMAN, SASCB      DATE   ]
 ]_____________________________________________________________________]
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 +_____________________________________________________________________
 ]                                                                     ]
 ]                       SUPPLEMENTAL SHEET                            ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ] AUTHOR:            ]                             ] DR:              ]
 ] HIRAM THOMPSON     ]    PASS PROGRAM NOTE        ]       37547      ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE: SEPT. 1987 ]
 ] LSIS/282-7225      ]      RELEASE NOTE( )        ] REV A: 09/11/95  ]
 ]____________________]_____________________________]__________________]
 ] TITLE:                                                              ]
 ]       RESTRICTIONS ON USE OF GPC MEMORY READ/WRITE CAPABILITIES     ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ]                                                                     ]
 ]    WHICH ALLOWS MULTIPLE HALFWORD PATCHING WITHOUT INTERRUPTION.    ]
 ]    SINCE THE "CONTIGUOUS" OPTION IS NOT AVAILABLE WITH THE ONBOARD  ]
 ]    GPC MEMORY SPEC, MULTIPLE HALFWORD PATCHING SHOULD BE AVOIDED    ]
 ]    WHEN USING THE ONBOARD SPEC. EXAMPLES OF POTENTIAL PROBLEMS      ]
 ]    INCLUDE:                                                         ]
 ]                                                                     ]
 ]    -IN A SINGLE GPC OR RS, PATCHING OF SUCCESSIVE HALFWORDS MAY     ]
 ]     NOT OCCUR CONCURRENTLY BUT BE INTERRUPTED BY OTHER PROCESSING   ]
 ]     WHICH MAY USE PARTIALLY PATCHED CODE OR DATA.                   ]
 ]                                                                     ]
 ]    -IN DISSIMILAR GPC'S OF A CS, PATCHING OF SUCCESSIVE HALFWORDS   ]
 ]     MAY NOT ONLY BE INTERRUPTED IN EACH GPC, BUT ALSO BE APPLIED    ]
 ]     AT DIFFERENT POINTS IN THE CS CODE WITHIN SET MEMBERS.          ]
 ]                                                                     ]
 ] C. THE PATCHING OF MULTIPLE CONTIGUOUS HALFWORDS USING THE          ]
 ]    "CONTIGUOUS" OPTION (ONLY AVAILABLE WITH UPLINK, TCS AND SACS)   ]
 ]    SHOULD BE AVOIDED IF THE PATCH IS TO BE APPLIED TO AN I/O AREA   ]
 ]    (MSC PROGRAMS, BCE PROGRAMS, AND I/O BUFFERS). THERE IS A        ]
 ]    POTENTIAL FOR THE IOP TO BE ACCESSING OR STORING INTO THESE      ]
 ]    AREAS WHILE THE PATCH IS TAKING PLACE.                           ]
 ]                                                                     ]
 ] VIOLATION OF THE RESTRICTIONS CAN RESULT IN A PATCH WHICH SOMETIMES ]
 ] WORKS BUT SOMETIMES DOES NOT. THIS IS DUE TO DYNAMIC INTERACTION    ]
 ] OF THE PROGRAM BEING PATCHED, THE PATCH PROGRAM, I/O ACTIVITY, AND  ]
 ] TIMER AND I/O INTERRUPTS. FAIL-TO-SYNC, DIVERGENT COMPUTATIONS, OR  ]
 ] COMPLETE LOSS OF THE PROGRAM ARE POSSIBLE RESULTS.                  ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ] USER RESPONSE:                                                      ]
 ]                                                                     ]
 ] DESIGN PATCHES TO ABIDE BY THE ABOVE RESTRICTIONS. EXCEPTIONS       ]
 ] SHOULD BE HANDLED ON AN INDIVIDUAL BASIS.                           ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]_____________________________________________________________________]
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