Prioritized demand multiplexing (PDM): a low-latency virtual channel flow control framework for prioritized traffic

We propose a new prioritized demand multiplexing (PDM) scheme for wormhole networks. Conventional demand multiplexing allows a set of ready flits to share a physical link in a strict round robin manner Thus, it does not allow flexibility for fast movement of high priority messages. The proposed PDM scheme allows a virtual channel, containing flits of a high priority message, to use its associated physical channel for multiple number of successive clock cycles. We present motivation behind the proposed PDM scheme, description of the scheme, and implementation issues. The study suggests that allowing a virtual channel with a high priority message to use 2 successive clock cycles is sufficient to provide up to 35% reduction in latency for high priority messages. The results demonstrate significant potential for designing high performance wormhole systems to support efficient implementation of applications with hybrid traffic characteristics.