On-chip routers typically have buffers dedicated to their input or output ports for temporarily storing packets in case contention occurs on output physical channels. Buffers, unfortunately, consume significant portions of router area and power budgets. While running a traffic trace, however, not all input ports of routers have incoming packets needed to be transferred simultaneously. Therefore, a large number of buffer queues in the network are empty and other queues are mostly busy. This observation motivates us to design router architecture with shared queues (RoShaQ), router architecture that maximizes buffer utilization by allowing the sharing multiple buffer queues among input ports. Sharing queues, in fact, makes using buffers more efficient hence is able to achieve higher throughput when the network load becomes heavy. On the other side, at light traffic load, our router achieves low latency by allowing packets to effectively bypass these shared queues. Experimental results on a 65-nm CMOS standard-cell process show that over synthetic traffics RoShaQ has 17% less latency and 18% higher saturation throughput than a typical virtualchannel (VC) router. Because of its higher performance, RoShaQ consumes 9% less energy per transferred packet than VC router given the same buffer space capacity. Over real multitask applications and E3S embedded benchmarks using near-optimal NMAP mapping algorithm, RoShaQ has 32% lower latency than VC router and targeting the same application throughput with 30% lower energy per packet.

On-chip router typically has buffers dedicated to its input or output ports for temporarily storing packets in case contention occurs on output physical channels. Buffers, unfortunately, consume significant portions of router area and power. While running a traffic trace, however, not all input ports of routers have incoming packets needed to be transferred at the same time. As a result, a large number of buffer queues in the network are empty while other queues are mostly busy. This observation motivates us to design RoShaQ, a router architecture that maximizes buffer utilization by allowing to share multiple buffer queues among input ports. Sharing queues, in fact, makes using buffers more efficient hence is able to achieve higher throughput when the network load becomes heavy. On the other side, at light traffic load, our router achieves low latency by allowing packets to effectively bypass these shared queues. Experimental results show that RoShaQ is 21% less latency and 14% higher saturation throughput than a typical virtual-channel (VC) router with 4% higher power and 16% larger area. Due to its higher performance, RoShaQ consumes 7% less energy per a transferred packet than a VC router given the same buffer space capacity.

This paper presents a globally-asynchronous locally-synchronous (GALS)-compatible circuit-switched on-chip network that is well suited for use in many-core platforms targeting streaming digital signal processing and embedded applications which typically have a high degree of task-level parallelism among computational kernels. Inter-processor communication is achieved through a simple yet effective reconfigurable source-synchronous network. Interconnect paths between processors can sustain a peak throughput of one word per cycle. A theoretical model is developed for analyzing the performance of the network. A 65 nm complementary metal-oxide–semiconductor GALS chip utilizing this network was fabricated which contains 164 programmable processors, three accelerators and three shared memory modules. For evaluating the efficiency of this platform, a complete 802.11a wireless local area network baseband receiver was implemented. It has a real-time throughput of 54 Mb/s with all processors running at 594 MHz and 0.95-V, and consumes an average of 174.8 mW with 12.2 mW (or 7.0%) dissipated by its interconnect links and switches. With the chip's dual supply voltages set at 0.95-V and 0.75-V, and individual processors' oscillators operating at workload-based optimal frequencies, the receiver consumes 123.2 mW, which is a 29.5% reduction in power. Measured power consumption values from the chip are within 2–5% of the estimated values.

The globally asynchronous locally synchronous (GALS) design style for a large area chip has become increasingly attractive due to the difficulty of designing global clocking circuits at high clock frequencies in the GHz range. In this paper, we present a high-speed interconnect network for a GALS multiprocessing system composed of a 2-D mesh array of processors. Processors are locally clocked by their own oscillators and communicate together using a static circuit-switched technique combined with a source-synchronous communication scheme. A technique to maximize the timing reliability on long-distance interconnects at high clock rates is proposed that is area and power efficient with low latency and allows a sustained ideal peak throughput of one word per cycle.

This paper presents a many-core heterogeneous computational platform that employs a GALS compatible circuit-switched on-chip network. The platform targets streaming DSP and embedded applications that have a high degree of task-level parallelism among computational kernels. The test chip was fabricated in 65nm CMOS consisting of 164 simple small programmable cores, three dedicated-purpose accelerators and three shared memory modules. All processors are clocked by their own local oscillators and communication is achieved through a simple yet effective source-synchronous communication technique that allows each interconnection link between any two processors to sustain a peak throughput of one data word per cycle. A complete 802.11a WLAN baseband receiver was implemented on this platform. It has a real-time throughput of 54 Mbps with all processors running at 594 MHz and 0.95 V, and consumes an average 174.76 mW with 12.18 mW (or 7.0%) dissipated by its interconnection links. We can fully utilize the benefit of the GALS architecture and by adjusting each processor's oscillator to run at a workload-based optimal clock frequency with the chip's dual supply voltages set at 0.95 V and 0.75 V, the receiver consumes only 123.18 mW, a 29.5% in power reduction. Measured results of its power consumption on the real chip come within the difference of only 2-5% compared with the estimated results showing our design to be highly reliable and efficient.