F10 unthrottles, but I think that will cause the game to run as
quickly as the machine will let it go... In most cases that is
unplayably fast.
You didn't mention the speed of the PC you're using. If other
similar-era games are running fine, you might have some kind of
configuration issue.
If you're running on a modest spec machine and lots of later games are
running slow, you can always revert back to an earlier version of
MAME. Versions below .100 (actually like .102 or whenever the sound
was overhauled) run a lot faster.
I'm running MAME 84 on a really old Pentium 3 machine and all the
Golden Age and most of the 90's stuff (Capcom beat 'em ups like
Punisher and scrolling shooters like Mars Matrix) runs great on it.