Diagnostics involve four important sub-categories.
  • Boot-up Diagnostics (Power On Selftest aka POST)

  • Run-time Diagnostics (Hardware Health Monitoring)

  • Online Diagnostics

  • Offline Diagnostics

Power On Self Test (POST) is the first task which verifies the hardware functionality of various modules during boot-up. Based on the criticality of the test, the selftest module decides whether to go ahead with the boot-up sequence of a particular subsystem or interface during a POST failure.

POST comprises of the following:

  • Memory BISTs (Built-in Self Test)

    This is to verify the memory block(s) present in the module and involves both internal and external memories.

    The memory tables are critical for proper functionality of the system, so any failures in these tests will result in the corresponding subsystem to be marked as "Failed" and thus that subsystem will not be available for use.

  • Front-end Port Loopback tests

    This is to verify the physical port front-end interface.

    These tests check if a particular interface can function properly. A test failure would mean that the particular interface is marked as "Failed" and thus it would become unavailable for use.