Sorry if this has already been covered, but I couldn't really find a definitive answer.
First, my specs:
core 2 duo 2.2ghz
4gb ram
HD4350
winxp pro 64bit
sony pvm
I have tried several games in groovymame and almost all of them are under 100% speed. I have attached a log for metal slug. it runs at 99.97%. I tried it in regular MAME and it ran at 100%.