abstract models of noc-based mpsocs for design space exploration
abstract models of noc-based mpsocs for design space exploration
abstract models of noc-based mpsocs for design space exploration
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that! JOSELITO! is! in! average! 2.3! times! faster! than! RENATO! in! 88%! <strong>of</strong>! the! executed! case! studies.!<br />
These! improvements! in! simulation! time! were! achieved! only! by! reducing! the! number! <strong>of</strong>!<br />
communication! events! originally! caused! by! the! flit! by! flit! <strong>for</strong>warding.! Currently,! JOSELITO! (code!<br />
optimization!without!losing!accuracy)!can!be!5S6!times!faster!than!RENATO.!!!<br />
!<br />
Table!V!!S!Speed!up!<strong>of</strong>!JOSELITO!in!comparison!to!RENATO.!<br />
! Uni<strong>for</strong>m! Normal! Pareto!OnNOff!<br />
! 2x2! 3x3! 4x4! 2x2! 3x3! 4x4! 2x2! 3x3! 4x4!<br />
T1! 2.51! 2.41! 2.93! 5.95! 2.00! 2.08! 2.45! 2.34! 2.34!<br />
T2! 2.52! 2.09! 2.27! 2.81! 2.01! 2.01! 2.54! 1.52! 1.64!<br />
T3! 2.53! 1.78! 1.99! 1.82! 1.39! 1.67! 1.78! 0.72! 0.74!<br />
T4! 4.07! 1.38! 1.68! 1.70! 1.14! 1.67! 4.71! 0.60! 0.70!<br />
4.6 Debugging and NoC Power Analysis using Scopes<br />
An! important! issue! in! the! <strong>design</strong>! <strong>of</strong>! complex! system! like! NoCS<strong>based</strong>! MPSoCs! is! the!<br />
debugging.!The!debugging!<strong>of</strong>!such!systems!is!difficult!and!time!consuming!because!<strong>of</strong>!the!intrinsic!<br />
lack!<strong>of</strong>!internal!observability!and!controlability!<strong>of</strong>!its!components![CIO08].!Thus,!more!appropriate!<br />
debugging! capabilities! to! <strong>design</strong>! NoCS<strong>based</strong>! MPSoCs! are! demanded! in! order! to! simplify! the!<br />
development!<strong>of</strong>!these!systems![MAR06][ZEN10].!In!this!context,!some!authors!propose!the!use!<strong>of</strong>!<br />
monitors,! which! can! be! attached! to! the! NoC's! components! (e.g.! router,! NI)! to! increase! its!<br />
observability,!as!well!as!to!collect!internal!per<strong>for</strong>mance!data!(e.g.!link!utilization)![CIO06][VER09].!<br />
The! collected! data! can! be! useful! to! improve! the! per<strong>for</strong>mance! evaluation! <strong>of</strong>! a! given! NoCS<strong>based</strong>!<br />
MPSoC,!<strong>for</strong>!instance,!optimizing!the!NoC!communication!usage!in!order!to!satisfy!the!application!<br />
requirements.!In!this!Thesis!an!actor!monitor,!called!Router/monitor,!was!developed!to!increase!<br />
the! NoC! model! observability! and! to! provide! the! necessary! in<strong>for</strong>mation! to! estimate! NoC! power!<br />
dissipation.!<br />
As!mentioned!be<strong>for</strong>e,!the!power!dissipation!imposed!by!the!NoC!interconnect!is!a!critical!<br />
challenge!in!MPSoCs!<strong>design</strong>.!As!classified!in!the!Chapter!3!<strong>of</strong>!this!Thesis,!NoC!power!dissipation!is!<br />
evaluated!<strong>based</strong>!on!three!power!estimation!<strong>models</strong>:!(i)!gateSlevel,!(ii)!volumeS<strong>based</strong>!model,!and!<br />
(iii)!the!adopted!rateS<strong>based</strong>!model.!The!NoC!power!estimation!<strong>based</strong>!on!the!first!model!(electrical!<br />
simulation)!is!accurate!when!compared!to!the!other!two!power!<strong>models</strong>.!However,!it!is!very!timeS<br />
consuming! due! to! the! number! <strong>of</strong>! details! that! must! be! considered! to! estimate! the! NoC! power!<br />
dissipation.! VolumeS<strong>based</strong>! <strong>models</strong>! estimate! the! average! power! as! a! function! <strong>of</strong>! the! total!<br />
transmitted! data.! There<strong>for</strong>e,! these! <strong>models</strong>! do! not! capture! lowSlevel! effects,! such! as! congestion!<br />
and! burstiness,! being! simple! but! inaccurate.! In! this! context,! the! rateS<strong>based</strong>! power! model! was!<br />
proposed!to!achieve!accurate!power!evaluation!by!considering!those!lowSlevel!effects.!<br />
4.6.1 Rate-<strong>based</strong> Power Model<br />
RateS<strong>based</strong>!power!estimation!model,!introduced!in![GUI08],!is!a!tradeS<strong>of</strong>f!between!volumeS<br />
<strong>based</strong>!and!gateSlevel!power!<strong>models</strong>:!data!volume!is!considered,!but!computed!as!a!transmission!