Scaling and performance of a priority packet queue for real-time applications

Real-time multiprocessor applications are typically characterized by hard deadlines which severely constrain interprocessor communications. Contention for communication resources and the use of first-in-first-out (FIFO) buffering can introduce priority inversion, resulting in missed deadlines. This paper investigates the scaling and performance of a novel 1.2 μm CMOS Priority Packet Queue (PPQ) design. Its unique segmented architecture effectively exploits the packetized nature of traffic within most real-time networks and achieves 96% the speed of a high-speed packet FIFO. The PPQ can either perform priority inheritance or overwrite lower priority packets during queue overflow, and robustly handles asynchronous read and write clocks of widely disparate frequencies. Comparison results show that the PPQ offers over twice the speed of the conventional design, and promises even greater relative speed improvement for larger designs