SLO-MO Playback

I've been editing on AVID since '95 and the other day a client asked me to do something I've never done before...no, not that! He wanted me to play the timeline in slow motion. Not a slow motion effect on a clip, but just playback in slow motion. I told him I could play it double, triple, or quadruple normal speed, but not slower than normal. Am I getting senile? Is this something I've forgotten from version 5.o? It seems like such a simple thing, but there's nothing in the manual and I can't remember ever doing it. Is it possible. Please enlighten me.