Hi wolfsoft,
GroovyMAME (recent versions) needs -throttle enabled for -syncrefresh to have effect. This is how MAME originally worked in the old days and why we recovered this behaviour. This way you can effectively toggle throttle ON/OFF by pressing F10 for benchmarking purposes without this option being locked by -syncrefresh. Don't be worried about scroll hiccups caused by -throttle being on, as is the case with main line MAME, this does not happen with GroovyMAME.