-di GPU indexes, default is all available GPUs. For example, if you have four GPUs "-di 02" will enable only first and third GPUs (#0 and #2).
Use "-di detect" value to detect correct GPU order for temperatures management (requires non-zero "-tt" option); note that it will not work properly if you do not want to assign all GPUs to miner.
You can also turn on/off cards in runtime with "0"..."9" keys and check current statistics with "s" key.
-gser this setting can improve stability on multi-GPU systems if miner hangs during startup. It serializes GPUs initalization routines. Use "-gser 1" to serailize some of routines and "-gser 2" to serialize all routines.
Default value is "0" (no serialization, fast initialization).