How-to for new evdisplay ( update Jan 11,2003)
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1. setenv ROOTSYS /apps/root/3.03-06-gcc3.04/root
2. setenv LD_LIBRARY_PATH ${ROOTSYS}/lib:${LD_LIBRARY_PATH}
3. start engine replay with parameters: rpc_on=1 rpc_control=n
   where 
    a) n=-1 means
    b) n= 0 means 
    c) n> 0 means every n events the engine will stop
   and wait for an RPC from the evdisplay