> Factory SerDes configuration for the P5020DS board is 0x36

Alright, so overall only 16 of 18 available lanes in use per factory default.

> Of course it is possible to modify the RCW to use another SerDes configuration.

Am I reading this right that the SerDes lanes are not fixed on the P5020DS board and can be re-assigned? So far I thought that a board designer had to decide for one of the available configurations and hardwire that one. Reconfigurability on a fabricated board would be even nicer, of course.