It is a product limitation. This expander chip supports dhpm up to 40 ports only, so PHY ports from 40 to 47 do not support 12G dhpm. It means that ARC-8028-32 slot 17-24 do not support 12G dhpm. This behavior does not happen on others Areca products.
Tags: ARC-8028-32, databolt, dhpm, edfb, PHY, slot