1. Network-on-Chip & NoCSim
Praveen Bhojwani

2. Agenda
Brief introduction
Development environment
Design components

3. Introduction
Future SoC designs will be too complex and bus based communication will be incapable of providing the desired level performance
On-chip networks address design issues

4. Possible NoC designs

5. Design Issues Regular network issues: topology Energy efficient
Latency aware
Reliable communication
Testability
Interfacing
etc

6. NoCSim Developed in SystemC Interconnection network simulator
Features:
Topology: 2D torus
Source routing
Virtual channel based communication
Capable of providing QoS, via class based VC allocation
Configurable multi-source traffic sources

7. Features (contd…)
Given energy estimates for certain components, can provide Energy and Power estimates for communication in the network
Can be setup to provide end-to-end or hop-to-hop reliability

8. Components InputChannel – input port OutputChannel – output port
VCAllocator – VC allocator
CNIntf – core network interface
NWTile – composed of IC, OC and VCA
NoC – 2D torus network of NWTiles

9. Components layout

10. Input Channel Receives flits Classifies them into VCs
Flits are flow digits
Packet is broken up into a number of flits
Each packet will have at least a HEAD and TAIL flit (if size==1, we have a HDT flit)
Classifies them into VCs

11. Input Channel (contd…)
Serves each VC in a round robin fashion
When serving HEAD flits (1st flit of a packet), requests VCAllocator for a VC at the next router
When providing QoS, it specifies the desired class
Forward flit to output channel in the desired direction
Also update credit information at the neighboring routers

12. Output Channel
Receives flits from Input Channels and sends them over the link to the next router
When providing reliability, it waits for ACK/NAK

13. VC Allocator
Receives VC requests for particular direction and class of service, returns free VC ids.
Accepts credit update information from Input Channels from all 5 directions

14. CNI – Core Network Interface
Acts as a traffic source and sink
Configured via configuration file
Active when system is setup for end-to-end reliability