The 4500-X started shipping in May 2012. From 4500-X white paper

    Advanced Quality of Service and Buffering

    Advanced QoS with up to eight configurable queues per port and customizable queue size per queue

    Active queue management through dynamic buffer limiting (DBL) to ensure bandwidth protection for low-rate critical and well-behaving flows such as voice traffic

    32 mega bytes of centralized buffering optimized to handle bursty video traffic and server microbursts, helping make sure that business-critical packets are not lost because of insufficient buffering

With control of the distribution of buffer memory across queues, it is possible to allocate all the beans to a single queue, making the switch behave like a on queue pony.