04-30-2015 11:13 AM
Strictly port count.
The 53124s has one less GbE copper port (with integrated PHY).
53124s has four 1GbE ports with integrated copper PHYs
53125s has five 1GbE ports with integrated copper PHYs.
The package/pinouts are the same. The pins for the 5th gbe port with integrated PHY on 53125s are NC on the 53124s pinout.
If you look at registers, etc, they are identical.