  In this paper we analyze the average queue backlog in a combined input-output
queued switch using a maximal size matching scheduling algorithm. We compare
this average backlog to the average backlog achieved by an optimal switch. We
model the cell arrival process as independent and identically distributed
between time slots and uniformly distributed among input and output ports. For
switches with many input and output ports, the backlog associated with maximal
size matching with speedup 3 is no more than 10/3 times the backlog associated
with an optimal switch. Moreover, this performance ratio rapidly approaches 2
as speedup increases.
