NoC frequency scaling with flexible-pipeline routers

Abstract

Abstract-Voltage and frequency scaling (VFS) for NoC can potentially reduce energy consumption, but the associated increase in latency and degradation in throughput limits its deployment. We propose flexiblepipeline routers that reconfigure pipeline stages upon VFS, so that latency through such routers remains constant. With minimal hardware overhead, the deployment of such routers allows us to reduce network frequency and save network energy, without significant performance degradation. Furthermore, we demonstrate the use of simple performance metrics to determine the optimal operation frequency, considering the energy/performance impact on all aspects of the system -the cores, the caches and the interconnection network.

Energy-efficient non-minimal path on-chip interconnection network for heterogeneous systems

“…In this section, we evaluate a heterogeneous multicore system as described in Section 4, with flexible-pipeline routers [23] as described in Section 3.1. We extend the system with DVFS support (Section 3.2) and non-minimal path routing (Section 3.3), and evaluate their impact on NoC energy consumption as well as overall system performance.…”

“…To avoid the latency increase of CPU traffic when passing through routers operating at lower frequency, we adopt the flexible-pipeline router design proposed in [23]. Voltage and frequency scaling (VFS) reduces router energy consumption at the cost of increase in packet transmission time, and degradation in throughput.…”

“…We follow the notation of slow down parameter S introduced in [23]. A slow down parameter indicates the router operating frequency.…”

“…In Figure 4(a), four routers operate at high voltage/frequency level and four operate at the low level; while in Figure 4(b), two routers operate at high voltage/frequency level, and the remaining six operate at medium level. Network energy is categorized into dynamic, static, and clock energy, where static and clock energy correspond to a significant potion of the total energy [10,23]. Static energy is proportional to supply voltage (V dd ), and clock energy is proportional to the product of V 2 dd and number of clock transitions.…”

“…Mishra et al [17] enabled DVFS on NoC routers to reduce the network power consumption. Flexible-pipeline [23] and variable-pipeline [8,16] routers are also proposed to save network energy while mitigating the latency penalties brought by network frequency reduction. Our work differs from previous work in that, we apply the DVFS technique in addition to flexible-pipeline routers, allowing aggressive voltage/frequency scaling without causing significant performance degradation.…”