power-aware and bist-aware noc reuse on the testing of core-based systems

Power-Aware and BIST-Aware NoC Reuse on the Testing of

Core-based Systems

Érika Cota Luigi Carro

Flávio Wagner Marcelo Lubaszewski

UFRGS

Porto Alegre, Brazil

b a c k n e x t h o m e

Context

SoC

core core core

corecorecore


Reuse Model

tester

SoC

core core core

corecorecore


Revisão dos principais objetivose fatores de sucesso

Improve the reuse the on-chip network as test access mechanism

minimal area overhead zero pin overhead feasible test time

Power consumption is an issue?

Optimal set of BISTed cores?

Goal


Revisão dos principais objetivose fatores de sucesso

NoC-based Test

Power consumption calculation

Modified scheduling

Considering BISTed cores

Experimental Results

Final Remarks

Outline


Access Paths Within the NoC

CUT 1

CUT 2

input

input

output

output



CUT

CUTCUT 2

CUT 1

input



CUT

CUTCUT 2

CUT 1

output



CUT

CUTCUT 2

CUT 1input



CUT

CUTCUT 2

CUT 1

input



CUT

CUTCUT 2

CUT 1

output


Parallelism Within the NoC

CUT 1

CUT 2

input

output

input

output


Pipeline Within the NoC

CUT 1

CUT 2

CUT 3

input

output

output

input



CUT 1

CUT 2

CUT 3

input

output

input

output



CUT 1

CUT 2

CUT 3

input

output

output

input



CUT 1

CUT 2

CUT 3

input

output

BOTTLENECKS!


Packets Scheduling

CUT 1

CUT 2

CUT 3

input

output


Reuse Algorithm

Define test packets

Define access paths for each core

Select a packet

Find available access path

Schedule packet


Power Consumption Calculation

Router

Core 2

Router

Core 3

Router

Core 4

Router

Core 5

Router

Core 6

wrapp

er

wrapp

er

wrapp

er

wrapp

er

wrapp

er

wrapp

er

Router

Core 1



Router

Core 2

Router

Core 3

Router

Core 4

Router

Core 5

Router

Core 6

wrapp

er

wrapp

er

wrapp

er

wrapp

er

wrapp

er

wrapp

er

Router

Core 1• F(#ffs, #gates, switching rate)• per cycle (any frequency)• per packet



Router

Core 2

Router

Core 3

Router

Core 4

Router

Core 5

Router

Core 6

wrapp

er

wrapp

er

wrapp

er

wrapp

er

wrapp

er

wrapp

er

Router

Core 1• F(length,width,switching rate)• per cycle (any frequency)



Router

Core 2

Router

Core 3

Router

Core 4

Router

Core 5

Router

Core 6

wrapp

er

wrapp

er

wrapp

er

wrapp

er

wrapp

er

wrapp

er

Router

Core 1

• F(#ffs, #gates, switching rate)• per cycle (any frequency)• per pattern


Power Consumption of One Packet

CUT

CUT

CUT 1

input

4*PW(router) + 3*PW(channel) + PW(CUT+wrapper)


Power-Aware Scheduling


Experimental Setup

SOCIN Network– under development at UFRGS– Grid topology– 32-bit channels– deterministic routing (XY)

ITC’02 SoC Test Benchmarks– d695, g1023– Placement for synthetic applications


Experimental Results - d695

Cores consumption >> wrapper consumptionT

est

time

Power Limit

0

10000

20000

30000

40000

50000

nolimit

50% 40% 30% 20% 10%

1 in / 1out

2 in / 2 out

3 in / 3 out

4 in / 4 out


Experimental Results - g1023

Cores consumption >> wrapper consumption

Inputs/Outputs

No powerLimit

50% 30% 20% 10%

1/1 52145 52145(0%)

52296(0.29%)

51853 33521

2/2 31898 31547(-1.1%)

33032(3.56%)

41016 67962

3/3 22648 24869(9.8%)

25873(14.2%)

37757 64557

4/4 18851 19776(4.9%)

31488(67%)

37871 66088


Experimental Results - d695

Cores consumption wrapper consumptionT

est

time

Power Limit

01000020000300004000050000600007000080000

nolimit

50% 40% 30% 20% 10%

1 in / 1out

2 in / 2 out

3 in / 3 out

4 in / 4 out


Experimental Results - g1023

Cores consumption wrapper consumption

Inputs/Outputs

No powerLimit

50% 30% 20% 10%

1/1 52145 835 - - -

2/2 31898 34355 61 61 -

3/3 22648 38598 102 61 -

4/4 18851 38633 158 61 -


BIST-Aware Scheduling

Each core has a BISTed version– 30% more area– 50% more power consumption– 2x the number of test vectors

All cores BISTed– system test time = largest test time among

cores– power consumption may be na issue


BIST-Aware Scheduling

1) All cores BISTed

– maximum parallelization

– minimum test time?

2) Define test scheduling considering power constraints

3) Replace the core with largest test time by its external tested version

4) Repeat 2 and 3 until test time increases


Experimental Results - p22810

No power constraints

BISTed Cores


Experimental Results - p22810

Multiple BIST model

BISTed Cores


Final Remarks

Alternative TAM for NoC-based SoCs

good trade-off test time x area X pin overhead even under power constraints (ETW’03)

Selection of the optimal set of BISTed cores for test time minimization (TRP’03)

Further selection of the best BIST method for the cores in the system

power-aware and bist-aware noc reuse on the testing of core-based systems

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