4500R chassis has a backplane speed of 24 Gbps.
So this means that if the X4548 line card was fully loaded with high-speed servers and start firing data into it, you'll get a 2:1 over-subscription. Next, Catalyst buffer size. The buffer size of all Catalyst switches were deliberately made small so as to distance itself as a closet switch chassis vs a data centre chassis (which the Nexus-series family of switches are meant and designed to be). So 200 Mbps may be around the right ballpark.
