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Dell EMC Configuration Guide for the S4048T–ON System 9.14.2.4

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LPC Bus Quality Degradation

LPC Bus Quality Analyzer (LBQA) runs on the system that make use of the LPC bus. It constantly monitors the LPC bus and alerts or warns the user using following methods when it detects signal degradation:

LBQA (LPC Bus Quality Analyzer) Failure Detection mode

  1. The system displays a high priority syslog message. The text of this syslog is CPU Clock signal has degraded below acceptable threshold on stack-unit <stack-unit-number> with service tag <service tag>. Please contact Technical Support. On chassis platforms, the text is CPU Clock signal has degraded below acceptable threshold on Line card <line card number> with service tag <service tag>. Please contact Technical Support. This syslog continues to show every 30 minutes. An SNMP trap with this information is also generated every hour.
  2. If SupportAssist is enabled - it sends the event message to the global SupportAssist server immediately and there after once in two days, so Dell can assist in pro-actively notifying and assisting customers.
  3. System Status LED changes to an alarm state, blinking amber for S3048–ON, S6100–ON and Z9100–ON, and solid amber for C9000. It is not possible to suppress this LED pattern until the unit is switched off (for RMA).
  4. The switch (control/management/data plane) continues to be active.
    NOTE This is true even if the unit is the master (in a HA chassis environment – as in the case of RPM) or a Stack master or standby (as in case of S3048-ON).
The following functions are performed as a part of this mode:
  1. The LBQA will be started as part of FTOS application init (typically as a poller in sysd).
  2. The LBQA will run as a fast poller (typically 1 sec) in failure detection mode.
  3. During every fast poll cycle, LBQA will be the first poller to run.
  4. In failure detection mode, the LBQA will issue a single IOCTL for each poll interval, which may in-turn issue multiple LPC operations (write & read-back) to check the sanity of the LPC bus using the scratch register.
  5. The LBQA will use an extended walking 1s/0s test along with a pattern based test (0x00, 0x55, 0xAA, 0xFF) that is staggered across several polls.
  6. The LBQA will limit each sanity check to a maximum of 16 operations (read + write).
  7. LBQA will use a variable number of sanity checks over time, it would perform at least 1 check during every poll interval but will perform 8 checks during a signal poll once in 5 seconds.
  8. The LBQA can be disabled on a system wide basis (i.e all stack-units or line cards as applicable) through a CLI command.

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