Machine-Check Detection .
Recovery Mechanisms .
Redundancy CorrectionCPU Retry
UnitDeletion Handling of Machine Checks
ContentsHandling of Invalid CBC in Storage Programmed Validation of Storage Handling of Invalid CBC in Keys in Storage Handling of Invalid CBC in Registers. Validation of Registers .
Check-StopState Machine-Check Interruption Conditions Repressible Conditions .
Exigent Conditions .
Machine-CheckInterruption Interruption Action. Point of Interruption Machine-Check Logout.
Machine-Check Handling
Machine-Check ExtendedInterruption Information Machine-Check Interruption Code.
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183Subclass .
Time ofInterruption Occurrence Storage Error Type .
Machine-CheckI nterruption Code Validity Bits.
Machine-Check Extended Logout Length
Machine-CheckControl Registers . Control Register 14 .
Check-StopControl Logout Controls. Machine-Check Subclass Masks Control Register 15 . Summary of Machine-Check Masking
The System/370 machine-check handling mecha
nism provides extensive machine-malfunction detec
tion to ensure the integrity of system operation, auto
matic recovery from some malfunctions, and report
ing by means of a machine-check interruption to
assist in maintenance and repair and in program
damage-assessment and recovery.
Machine-Check Detection
Machine-check detection mechanisms may take
many forms, especially in control functions for arith
metic and logical processing, addressing, sequencing,
and execution. For program-addressable informa
tion, detection is normally accomplished by encoding
redundancy into the information in such a manner
that most failures in the retention or transmission of
the information will result in an invalid code. The
encoding normally takes the form of one or more
redundancy bits appended to a group of information
bits. These redundancy bits are referred to as"check bits." The group of data bits and the associated
check bits are called the"checking block. " The inclusion of a single check bit in the checking
block allows the detection of any single-bit failure
within the checking block. In this arrangement, the
checking bit is sometimes referred to as a"parity bit. " In other arrangements, a group of check bits is
included, increasing the checking power and, in some
cases, providing sufficient redundancy to permit
both detection and correction.
For checking purposes, the entire content of a
checking block, including the redundancy, is called a
"checking blockcode" (CBC). When a CBC com
pletely meets the checking requirements (that is, no
failure is detected), it is said to be valid. When both
detection and correction are provided and a CBC is
not valid but satisfies the checking requirements for
correction (the failure is correctable), it is said to be
near-valid. When a CBC does not satisfy the check
ing requirements (the failure is uncorrectable), it is
said to be invalid.
Machine-Check Handling 171
Recovery Mechanisms .
Redundancy Correction
Unit
Contents
Check-Stop
Exigent Conditions .
Machine-Check
Machine-Check Handling
Machine-Check Extended
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Time of
Machine-Check
Machine-Check Extended Logout Length
Machine-Check
Check-Stop
The System/370 machine-check handling mecha
nism provides extensive machine-malfunction detec
tion to ensure the integrity of system operation, auto
matic recovery from some malfunctions, and report
ing by means of a machine-check interruption to
assist in maintenance and repair and in program
damage-assessment and recovery.
Machine-Check Detection
Machine-check detection mechanisms may take
many forms, especially in control functions for arith
metic and logical processing, addressing, sequencing,
and execution. For program-addressable informa
tion, detection is normally accomplished by encoding
redundancy into the information in such a manner
that most failures in the retention or transmission of
the information will result in an invalid code. The
encoding normally takes the form of one or more
redundancy bits appended to a group of information
bits. These redundancy bits are referred to as
check bits are called the
block allows the detection of any single-bit failure
within the checking block. In this arrangement, the
checking bit is sometimes referred to as a
included, increasing the checking power and, in some
cases, providing sufficient redundancy to permit
both detection and correction.
For checking purposes, the entire content of a
checking block, including the redundancy, is called a
"checking block
pletely meets the checking requirements (that is, no
failure is detected), it is said to be valid. When both
detection and correction are provided and a CBC is
not valid but satisfies the checking requirements for
correction (the failure is correctable), it is said to be
near-valid. When a CBC does not satisfy the check
ing requirements (the failure is uncorrectable), it is
said to be invalid.
Machine-Check Handling 171