1. An arrangement comprising: storage means organized as a queue having a head end and a tail end, the storage means including a plurality of storage locations for holding queue entries; means for storing a queue entry received for processing, in a free at least one location at the tail end of the queue; means for determining whether the stored tail end entry is invalid; means responsive to the determining means for freeing the at least one location holding an invalid tail end entry to hold a new tail entry; means for retrieving a stored queue entry for processing from the head end of the queue; means for determining whether the queue is empty; and means, coupled to the retrieving means and cooperative with the means for determining whether the queue is empty, for obtaining a retrieved entry from the retrieving means when the queue is determined not to be empty, and for receiving an entry for processing directly, by bypassing the queue, when the queue is determined to be empty.