Reducing power and latency in 2-D mesh NoCs using globally pseudochronous locally synchronous clocking

ABSTRACT

One of the main problems when designing large ASICs today is to distribute a low power synchronous clock over the whole chip and a lot of remedies to this problem has been proposed over the years. For Networks-on-Chip (NoC), where computational Resources are organised in a 2-D mesh connected together through Switches in an on-chip interconnection network, another possibility exists: Globally Pseudochronous Locally Synchronous clock distribution.In this paper, we present a clocking scheme for NoCs that we call Globally Pseudochronous Locally Synchronous, in which we distribute a clock with a constant phase difference between the switches. As a consequence of the phase difference, some paths along the NoC switch network become faster than the others. We call these paths Data Motorways. By adapting the switching policy in the switches to prefer data to use the motorways, we show that the latency within the network is reduced with up to 40% compared to a synchronous reference case.The phase difference between the resources also makes the circuit more tolerant to clock skew. It also distributes the current peaks more evenly across the clock period, which lead to a reduction in peak power, which in turn further reduces the clock skew and the jitter in the clock network.

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INDEX TERMS

Primary Classification:
  B. Hardware
  B.7 INTEGRATED CIRCUITS
      B.7.1 Types and Design Styles
          Subjects: VLSI (very large scale integration)

Additional Classification:
  B. Hardware
  B.6 LOGIC DESIGN
      B.6.1 Design Styles
          Subjects: Combinational logic

General Terms:
Design

Keywords:
GALS, GPLS, clocking, hot-potato, mesh, network on chip, pseudochronous