While looking into why a several EMs on a SX controller aren't running at the configured scan rate, fell into a rabbit hole.
In the past, have trended controller parameters such as HPCTONTIME.CV, COMM/AWSNT.CV, and FRETIM to get perspective.
Of more recent times, Diagnostics' Performance Index Parameter ostensibly aggregates the most salient metric parameters into a single value from 1 to 5.
This SX controller has 50% of modules running above configured scan rate and yet FRETIME, H, M, and LPCTONTIME all at 100% - and yet Performance Index Parameter = 4 (Good)
How does one reconcile these metrics and yet consequential module scan time slippage?