To keep an eye on the temp while testing overclocking I found it useful to use putty to ssh into retropi and run this command combo from the pi home directory ctrl-c will exit from it
while true;do vcgencmd measure_temp; sleep 5; done
this will print out the temp every 5 seconds
I also found it useful to log to a file so I could focus on playing and when it froze the file was there to review.
while true;do vcgencmd measure_temp; sleep 5; vcgencmd measure_temp >> templog.txt; done
log file can be reviewed by using nano templog.txt