@mitu when the crash happen, i hard reset then restart the system as i can't get a tty in a freeze status.. so i go like you suggest me to get log from /dev/shm/runcommand.olg but i can't find nothing. infact as sometime get no crash i find there the log without error as a list the operation in the retropie like type of emulator rom launched etc. so crash without log or log without crash.
i can't go further..infact i can't understand what happened different when one time things go perfect ( sometime i change the kernel ... but second chances to run other rom all crash so i think is not depending on this ) i don't know if depend on using a particular type of emulator : neo geo or version of mame and i don't know, it's own configuration ( video settings, audio .. ) but i can't get log after crash ... so i dont know to proceed to fix. have a nice day and thnx for all the detailed reply.