OASIS NoC Revisited

Adam Esch (m5148108)

Outline

• Pre-Research• OASIS Overview• Research Contributions• Remarks• OASIS Suggestions• Future Work

Pre-Research

• Before working with OASIS, I had to– Learn Verilog– Adjust to Quartus II/ModelSim– Analyze OASIS

OASIS Overview

• OASIS, just like all other NoCs, has a set of configurable parameters.

Parameter Default Value

Network Size 4x4 (Mesh)

Buffer Depth 4

Routing Algorithm Deterministic XY

Flow Control Scheme Stall/Go

Forwarding Method Wormhole Switching

FLIT Size 76-bit (12-bit header, 64-bit payload)

OASIS Network

• Each router has five input ports (Local, North, East, South, West) and five STALL/GO links

• Each router is addressed by its physical location (Y,X)

00 10 20 30

01 11 21 31

02 12 22 32

03 13 23 33

OASIS Router

• Each router consists of three important stages– Routing– Switch

Allocation– Crossbar

Traversal

Research

• I analyzed– resource utilization for different network sizes– transmission latency using a random number

generator

Resource Utilization• Target Devices:

– Cyclone II EP2C35F672C6– Stratix III EP3SL150F1152C2

• Flit Payload = 8 bits• Design Tools = Quartus II ver 9.1

Transmission Latency (1/2)

Transmission Latency (2/2)

• The network behaves similarly in each case

• Transmitting more FLITS does not have a major effect on latency

• Packets sent from 01 will always have a longer latency than those sent from 10 because of round robin scheduling

Remarks

• The size of the FLIT payload does not seem to affect latency

• I was unfortunately unable to implement a random number generator for 3x3 or 4x4 networks, but I expect they would behave the same

OASIS Suggestions

• Deterministic Routing can be improved– Semi-Adaptive Routing is the logical next step

• As networks become larger, mesh topologies become inefficient– Creating a router ‘hierarchy,’ like the internet

employs, is much more efficient

• Assuming the network size is kept constant, the header length can be shortened. It would save a small number of resources.

Future Work

• I plan to continue research in NoC, semi-independently, when I return to America.

• From prior studies, I am interested in clustering and subnetting

• Ordered transmission defeats the purpose of a packet switched network. I would like to study the reorder buffers