This document discusses runtime reconfigurable network-on-chips (NoCs) for field programmable gate arrays (FPGAs). It describes several NoC architectures that support dynamic exchange of hardware modules through partial reconfiguration of FPGAs, including DyNoC, CuNoC, QNoC, CoNoChi, ReNoC, and RecoNoC. It also discusses the design factors, quantitative metrics, and applications of runtime reconfigurable NoCs, and concludes that these NoCs provide interconnect frameworks with reconfiguration capabilities, flexibility, and performance to integrate multiple applications on a single FPGA.

1. Runtime Reconfigurable Network-on-chips
for FPGA-based systems
Mugdha Puranik
Department of Electrical and Computer Engineering
mpuranik@rams.colostate.edu

2. 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)

3. Partial Reconfiguration of FPGA
Static
modules
Static region
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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
FPGA
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PRR 1
PRR 2
Modules: A & B
Modules: C & D

4. Design Factors
Quantitative Metrics
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Throughput
Latency
Area
Interconnect Utilization
Power and energy consumption
Crucial Characteristics
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Scalability
Extensibility
Modularity
Flexibility

5. Architectures
Communication Architectures which support
dynamic exchange of hardware modules

6. DyNoC-Dynamic Network-on-chip
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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

7. CuNoC
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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

8. QNoC
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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

9. CoNoChi-Configurable NoC
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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

10. 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

11. RecoNoC
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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

12. Programmable NoC Router RANoC
• Router architecture of Network on
chip (RANoC)
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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

13. PNoC
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Subnets containing router and network
nodes, which can be replaced
dynamically
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Router performs circuit switching of the
nodes
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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

14. 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

15. Fault Tolerant Reconfigurable NoC-based SoC
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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

16. Hardwire NoC On Future FPGAs
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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

17. Design Flow for NoC-based devices
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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

18. 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

19. Application Mapping To Use Case Execution
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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

20. 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

21. References
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