Global traffic control system for unbalanced data flow on nonsquare event builder in BELLE experiment

It has been stated that an unbalanced data flow cannot be handled by blocking switches such as a barrel shifter. It is not true for a square switch, which has the same number of destination nodes as source nodes. However, if the switch is not square, a simple barrel shifter is not adequate. We have studied the minimal switch configuration for the event builder system in a BELLE experiment in KEK. The performance in the actual experiment was measured.