Runtime Reconfigurable Network-on-chips for FPGA-based systems

Mugdha PuranikDepartment of Electrical and Computer Engineering

mpuranik@rams.colostate.edu

Introduction

• Need of reconfigurable hardware for Embedded System devices

• Flexibility provided by Field Programmable Gate Arrays (FPGAs)

• Need to suitable communication architecture

• Runtime reconfigurable Network-on-chip (NoC)

Partial Reconfiguration of FPGA

• The partial bit files can be downloaded to modify the reconfigurable regions to change the functionality or just some parameters, without compromising the integrity of applications running on other parts

• Static logic and Reconfigurable logic

• Partial bitstreams downloaded via Slave SelectMAP, Slave Serial, JTAG, or Internal Configuration Access Port

FPG

A PRR 1

PRR 2

Sta

tic

regio

n

Static modules

Modules: A & B

Modules: C & D

Design Factors

Quantitative Metrics Throughput Latency Area Interconnect Utilization Power and energy consumption

Crucial Characteristics Scalability Extensibility Modularity Flexibility

Architectures

Communication Architectures which support dynamic exchange of hardware modules

DyNoC-Dynamic Network-on-chip

• Packet based NoC

• 2D array of processing elements and router

• Routers inside the boundary of the modules are redundant and can be used as additional resources to implement bigger modules

• S-XY routing

CuNoC

• Enhances the architecture of DyNoC

• CU receives upto 4 packets at a time and has one buffer for all

• Determines the transfer schedule according to priority-to-right rule

• Two types: (1)Classic CU (2) To-give-way Cugw

• High performance and low area overhead

QNoC

• QNoC also allows dynamic placement of modules in 2D mesh topology and computes path from source to destination during runtime

• Q-switch : Input registers, Routing Block, Output Logic, Control Logic

• Yields higher throughput due to additional intelligent logic of Q-switch

CoNoChi-Configurable NoC

• Virtual cut through switches with four equal full duplex links

• FPGA is partitioned into grid of rectangular subareas

• Network size and topology can be changed at runtime

• Supports physical and logical addresses

• Less number of switches, saves area, reduces latency

ReNoC-Reconfigurable NoC

• Configurability is inserted as a layer between routers and links

• Energy-efficient topology switches

• ReNoC is that it uses both energy efficiency of circuit switching and flexibility of packet switching

• Clock gating and power gating for unused switches and links

• Compared to static NoC, application specific reconfigurable architecture ReNoC leads to 56% power reduction

• Dynamic reconfigurability of FPGA to create shortcuts from source to destination

• Additional I/O port in crossbar

• TMAP datafolding toolflow to automatically generate RecoNoC

Reduced reconfiguration time Smaller area

RecoNoC

Programmable NoC Router RANoC

• Router architecture of Network on chip (RANoC)

Network processor on chip (NPoC) Reconfigurable crossbar switch (RCS) Decoder unit Arbiter unit Input buffer and buffer access unit

• NPoC configures RCS, RCS adapts its topology

• Compared to a conventional NoC (SoCIN), RANoC is smaller and consumes less power

• Power efficient, fast adaptable router

PNoC

• Subnets containing router and network nodes, which can be replaced dynamically

• Router performs circuit switching of the

nodes • PNoC topologies

• Routing table is maintained to establish connections between modules

• Advantages: high communication rates, low latencies, simpler

• Disadvantages: wasted bandwidth, poor scalability, setup latencies

DRNoC: For Fast System Emulation

• Reconfigurable platform which accelerates the design space exploration

• Cores are dynamically allocated to REs (Reconfigurable Elements)

• Different DRNoC configurations are downloaded in FPGA and emulated

• Advantages No synthesis needed Reconfiguration time in range of

microseconds Online traffic measurement allows

tracking network dynamics

Fault Tolerant Reconfigurable NoC-based SoC

• Each tile holds a core container and cache memory

• NoC is circuit switched

• Tasks are allocated dynamically and identified using tasks identifier

• Randomness in runtime mapping of tasks and in route selection: tolerant to faults in interconnections and cores

• User-aware task allocation & cache memory in tiles: runs tasks with higher temporal locality faster

Hardwire NoC On Future FPGAs

• Hardwire NoC to support the dynamic reconfigurability of FPGAs

• Additional routing resource

• Advantages Saves valuable reconfigurable resources High speed due to high bandwidth Reduced power consumption Simplified design

Design Flow for NoC-based devices

• Need: to reduce design and testing time

• Advantages of automating designing of reconfigurable NoC efficient resource utilization reliable and fast verification and design space exploration effective testing for system debugging

Example of Design Flow

Phases Requirement capturing Interconnections needed Mapping: Communication architecture

Routing: All routes needed

Placement: Reconfigurable regions in grid

Final solution selection

Outputs XML files-output of every

intermediate step SystemC files-used for simulation VHDL files-define reconfigurable

architecture Bitstreams-used to configure FPGA

Application Mapping To Use Case Execution

• Reconfigurations needed after mapping of applications executing a particular use case

• Minimum reconfiguration overhead, area-efficiency, eliminate re-synthesis

• NoC based MPSoC synthesis

• Load and compile program codes on processors

• Possible NoC configurations are stored in controlling processor

Conclusion

• To integrate multiple applications on single FPGA

• Reconfigurable NoCs- interconnect framework, reconfiguration capabilities, flexibility and performance

• Guide in deciding one or the other interconnection architecture

• Motivate development of novel reconfigurable communication architectures

References

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FPL, 200422. M.Huebner et al., “Exploiting Dynamic and Partial Reconfiguration for FPGAs — Toolflow, Architecture and System Integration”,

SBCCI, 200623. Partial Reconfiguration User Guide-Xilinx24. Zeferino et al., “SoCIN: a parametric and scalable network-on-chip”, Integrated Circuits and Systems Designs, 200325. C.L Chou et al., “User-aware dynamic task allocation in networks-on-chip”, DATE, 2008