Memory channels under-populated

The board exposes more memory channels than have DIMMs installed (or DIMMs run below rated speed), so peak memory bandwidth is reduced. On EPYC-class boards the alert also flags placement, when the installed DIMMs double up on adjacent channels (one memory-controller group) instead of spreading one per group; the same DIMM count placed wrong idles controllers and weakens interleaving. Not a fault; a hardware-population advisory. Fix is physical DIMM installation or rebalancing during a maintenance window, per the board manual's population table.