Here is an auction of what I meant.
http://cgi.ebay.com/ws/eBayISAPI.dll...853090859&rd=1
They're basically meant for machines that do not have a reversing spindle. They work pretty good as long as you compensate Z correctly for the floating head for blind holes.
We have 2 machines that have the 2100 control. Unfortunately I haven't had the opportunity to run either. One is a Cinncinati 3 spindle 5 axis gantry. The other is a high speed 5 axis VMC.