Quality-of-Service (QoS) for Asynchronous On-Chip Networks A thesis submitted to the University of Manchester for the degree of Doctor of Philosophy in the Faculty of Science and Engineering 2004 Tomaz Felicijan Department of Computer Science 1 Contents Contents ...................................................................................................................2 List of Figures .........................................................................................................6 List of Tables ...........................................................................................................8 Abstract ...................................................................................................................9 Declaration ............................................................................................................10 Copyright ...............................................................................................................10 The Author ............................................................................................................11 Acknowledgements ...............................................................................................12 Chapter 1: Introduction ....................................................................................13 1.1 Thesis overview ......................................................................................17 1.2 Research contributions ...........................................................................18 Chapter 2: Asynchronous Logic .......................................................................20 2.1 Introduction ............................................................................................20 2.1.1 Advantages of asynchronous logic ..............................................22 2.1.2 Disadvantages of asynchronous logic ..........................................24 2.2 Asynchronous design methodologies .....................................................25 2.2.1 Delay-insensitive circuits .............................................................26 2.2.2 Quasi delay-insensitive circuits ...................................................26 2.2.3 Speed-independent circuits ..........................................................27 2.3 Handshaking protocols ...........................................................................27 2.3.1 Non return-to-zero handshaking protocol ....................................28 2.3.2 Return-to-zero handshaking protocol ...........................................29 2.4 Data encoding .........................................................................................29 2.4.1 Single-rail encoding .....................................................................29 2.4.2 Delay-insensitive encoding ..........................................................30 2.5 The Muller C-element ............................................................................31 2.6 Metastability ...........................................................................................33 2.7 Large-scale asynchronous design ...........................................................34 2.8 Summary .................................................................................................36 Chapter 3: Quality-of-Service (QoS) ................................................................37 3.1 Introduction ............................................................................................37 3.1.1 QoS: a user’s view .......................................................................38 3.2 Basic QoS architecture ...........................................................................38 3.3 End-to-end QoS levels ............................................................................38 3.4 QoS control methods ..............................................................................39 3.4.1 Overprovisioning .........................................................................40 3.4.2 Buffering ......................................................................................40 3.4.3 Traffic shaping .............................................................................41 3.4.4 Resource reservation ....................................................................42 3.4.5 Admission control ........................................................................46 3.5 Summary .................................................................................................47 Chapter 4: Networks-on-Chip (NoCs) .............................................................48 2 4.1 Introduction ............................................................................................48 4.2 NoC design issues ...................................................................................50 4.2.1 Wiring resources ..........................................................................50 4.2.2 Power consumption ......................................................................51 4.2.3 Modularity ....................................................................................51 4.2.4 Hardware costs .............................................................................51 4.3 OSI reference model applied to NoCs ....................................................52 4.4 NoC services ...........................................................................................54 4.4.1 Data integrity ................................................................................55 4.4.2 Lossless data delivery ..................................................................55 4.4.3 In-order data delivery ...................................................................55 4.4.4 Time-related guaranteed services .................................................56 4.5 QoS for on-chip networks .......................................................................56 4.5.1 Guaranteed services .....................................................................56 4.5.2 Best-effort services ......................................................................56 4.6 QoS for asynchronous networks .............................................................58 4.6.1 Reserving network bandwidth .....................................................58 4.6.2 Buffer management ......................................................................62 4.6.3 Admission control ........................................................................63 4.7 Summary .................................................................................................63 Chapter 5: The Network Layer ........................................................................65 5.1 Introduction ............................................................................................65 5.1.1 Direct networks ............................................................................65 5.2 Network topology ...................................................................................67 5.3 Switching ................................................................................................69 5.3.1 Circuit switching ..........................................................................69 5.3.2 Store-and-forward and virtual cut-through switching ..................70 5.3.3 Wormhole switching ....................................................................70 5.4 Routing ...................................................................................................70 5.4.1 Algorithmic routing ......................................................................71 5.4.2 Source routing ..............................................................................73 5.4.3 Dimension-ordered routing algorithm .........................................73 5.5 Packet size and organization ...................................................................73 5.6 QoS architecture .....................................................................................74 5.6.1 Principle of operation ...................................................................75 5.6.2 Bandwidth allocation ...................................................................76 5.7 Summary .................................................................................................77 Chapter 6: The Data Link Layer ......................................................................78 6.1 Data integrity ..........................................................................................78 6.2 Flow-control ...........................................................................................79 6.3 Medium access control ...........................................................................80 6.3.1 Asynchronous arbitration .............................................................81 6.3.2 Proposed solution .........................................................................82 6.3.3 Principle of operation ...................................................................83 6.3.4 Implementation ............................................................................84 6.4 Summary .................................................................................................87 Chapter 7: The Physical Layer .........................................................................88 3 7.1 Introduction ............................................................................................88 7.1.1 Power