If I have several hair groups on a character do I have to run the dynamics calculations for each individual group. Or does the simulation work on all groups at the same time?  As it is one simulation does not seem to affect many of my hair groups. 
Pete

You have to run the dynamics calculations for each individual group.
You can also choose in the menu: Animation-> Recalculate Dynamics -> All Hair, that will run all calculations. Be prepared to wait for a while, though: that can take some time. Better get yourself a fresh cup of coffee (or, if you're unlucky, you can fly to Brazil, pick your own coffee, dry and roast it, and maybe then the calculations will be done...).

with poser dynamic hair, if collision is on, the simulation takes a long time. I have learned to avoid the requirment for collision by using only hairstyles that "stand out" from the head/face because of "position strength" or 'root strength."  Even then, sim can take a long time.

Also, be sure "Show Populated" is UNCHECKED for each group before you run your sim.

::::: Opera :::::

Jeesh. Because the controls in the hair room do not actually allow for control of the hair that much...at least as far as I can tell... I broke down the  head into as many as 10 groups. Not counting the sides of the head. I did this because for example lets say I slit the head into just two groups. I have found it impossible to select only some of the hair to reposition.  Select  only the front hairs and  the rear hairs become selected too. And even then not all the hairs that you surronded by your selection box become selected. Similarly I found it impossible to "deselect" hairs. Its always "almost all or none". I've seen Dr. Geeps web page all abouty the hair room. But A) it is hard to follow. B) it pretty much only explains the dials. It does not offer up a methodology to creating hair. So I am at a loss as to how to creat nice hair on a head. Even if I choose some simplistic hair like unstyled straight,  long hair that is to drape over the shoulders and flow to the middle of the back.

One thing that drives ne insane. How the hell do I stop the sim? constantly clicking or holding the cancel key does nothing. Constantly clicking or holding the escape key also does nothing.

Man I guess to do a worth while simulation one would need a Xenon processor or whatever the top ones are. And maybe even two of them. Only 5,000 hairs  with 24 vertices and its only calc'ed 21 frames over 10 hours with collision on. "Ahow pop" was unselected too.  I have 1.9Ghz Athlon with 1.5gig of ram. Ya gotta have collision  on or the hair will pass the the body I would imagine. It's just pathetic. The needs of the sim as well as my PC.
Pete

A good way to reduce calculation time A LOT is using a hair proxy.
What is a hair proxy? A very low-res figure with the same shape as your "real" figure, a figure that you make invisible when you render.
The trick is to let the hair collide against this proxy figure, not against the "real" high-poly figure.

kirwyn has several hair proxies in freestuff (Jessi, V3 and V4) and more in the marketplace. The hair proxies easily reduce calculation times by a factor of 10-100.

Cool I'll check it out