GSRC Annual Symposium September 28 & 29, 2006 Faculty: Kahng, Markov, Orshansky, Sylvester GSRC...

GSRC Annual Symposium

September 28 & 29, 2006

Faculty: Kahng, Markov, Orshansky, Sylvester

GSRC Annual Symposium

September 28 & 29, 2006

Faculty: Kahng, Markov, Orshansky, Sylvester

System-Level Living RoadmapSystem-Level Living Roadmap

September 28, 2006 GSRC Annual Symposium2

System-Level Living Roadmap• Only cost-effective technology innovations reach production

– What are relevant bounds, and how do they evolve?– What are quantified benefits from available technology options?– Beyond-ITRS: what are system implementation roadblocks?

• System-level design optimization and scaling– What are the relevant models and metrics for system scaling?

• Early analysis tools– Map technology concerns (power, variability, speed, area, …) to

system concerns (total cost, availability, …)

• Roadmaps– Connect applications to design and process technologies

well-calibrated cost and resource tradeoffs


Technology / Circuit Data

Fmax Variability

Statistical Clock Skew SER Macromodeling

Variability Data

Roadmap of Parametric Yield Estimation and Optimization: TUNES


Roadmap of Parametric Yield Estimation and Optimization: Block-Level Probabilistic Power-Delay Exploration

• Variability greatly impacts leakagepower and parametric yield– Exponential dependency on process

• Package often sets power limits– Cooling costs grow rapidly for higher power

Minimum Ship Frequency

Design Spread SlowFast

Po

wer

Cooling/Power Limit

Max Ship Freq(No Leakage)

Power w/Leakage

SwitchingPower

Nu

mb

er o

f P

arts Leakage

Max Ship Freq(With Leakage)


Roadmap of Parametric Yield Estimation and Optimization: Block-Level Probabilistic Power-Delay Exploration

• How much parametric yield loss can be recovered?

• DAC-05 Best Paper: Robust LP, second-order conic programming for sizing / dual Vth

– Efficient, large-scale parametric yield maximization

• Designer chooses sweet spot in power-delay space, trades timing yield for power yield, etc.

– E.g., 5% timing yield loss 25% less power

Statistical Optimization

Deterministic Optimization

Statistical Optimization

Deterministic Optimization

0 200 400 600

Fre

qu

ency

Static Power ( μW )

0.60 0.61 0.62 0.63 0.64 0.66 0.67

600

650

700

750

800

850

900 Deterministic optimization Statistical: inter and intra-chip variation Statistical: all intra-chip variation

To

tal P

ow

er (W

)

Delay (ns)


Roadmap of Reliability: Impact of Dynamic Reliability Management

• TDDB, EM, thermal cycling, NBTI with dynamic stress inputs• PID + threshold control solution• DRM voltage control

– Boosts/throttles maximum assignable voltage– +25% peak performance with typical workload/temperature

• +12-15% peak performance workloads

• +10-12% peak performance temperature

• Future directions– Parametric performance

degradations vs. hard failures– Sensor architecture and

placement– ElastIC: A system-level

adaptive architecture

0 2 4 6 8 10 12

x 104

0.6

0.8

1

1.2

1.4

1.6

1.8

0 2 4 6 8 10 12

x 104

0

0.5

1

1.5

2

2.5

3x 10-9

VDD

DamageDRM Damage Curve

Time

Lifetime Budget Curve

DVS Damage Curve

In a DRM System, the maximum voltage can be “boosted” to allow periods of higher peak performance while maintaining a margin below the budgeted damage curve.

In a DRM System, the maximum voltage can be “boosted” to allow periods of higher peak performance while maintaining a margin below the budgeted damage curve.

“Boost”“Boost”


Roadmap of Reliability: Efficient Soft Error Analysis and Optimization in Combinational Logic

• Proposed algorithm considers injection, propagation, and merging of SET descriptors (capturing correlation between transient waveforms and rate distribution function) in STA-like fashion– Waveform models based on Weibull, 1-time characterization cost

• Highly efficient: runtime linear with #gates (25K gates in 0.2sec)• Accurate: ~15% error in FIT• vs. Monte-Carlo SPICE

• Used in SER optimization

• Gate sizing + flip-flopassignment shows 28X SER reduction with nodelay penalty and 5% area overhead– Runtime: 1 min

for 5K gates

Q0 {Q1, Q2, …, Qm}

Qm

Q1V

olt

age

(V)

Time (ps)

Rate Function

Ra

te R

Qm

Q2

Q1

R2

Rm

R1

Charge Q

Transient Injection

SET Descriptor(d0,d1)

Vector bVector R Waveform Parameters

Q0 {Q1, Q2, …, Qm}

Qm

Q1V

olt

age

(V)

Time (ps)

Rate Function

Ra

te R

Qm

Q2

Q1

R2

Rm

R1

Charge Q

Transient Injection

SET Descriptor(d0,d1)

Vector bVector R Waveform Parameters


Roadmap of Reliability: Bottom-Up Reliability Prediction

• System-level analysis requires:– Precise gate electrical

properties– Logical structure of the circuit– System-level timing behavior Electrical, logical, and timing

window masking• Cell library characterization• Intractability (#P) of logical

masking– Pioneered use of decision

diagrams in this context– DATE-05 Best Paper award

• Three new static SER analysis tools

• Pulse Generation: – Library: Output Waveform = f(Collected

Charge)

CCLLA=0

B=1

Y 00 PWPWVVthth

LibraryLibraryLibraryLibrary

00 PWPWininCCLL

A

B=1

Y

VVthth

VVthth

• Pulse Propagation: – Library: Output Waveform = f(Input

Waveform)

LibraryLibraryLibraryLibrary


Roadmap of Reliability: Fast Analysis of Soft Error Susceptibility (FASER) for Cell-Based Designs

0

0.1

0.2

0.3

0.4

0.5

0.6

1 2 3 4 5 6 7

Logic Depth

So

ft E

rro

r R

ate

s (

a.u

.)

With Logic Masking

Without Logic Masking

1

n2

Tclk

Output (V)

t

Cload

Input (V)

t

1.2

0.6

0

0 50 100 0 50 100

Vo

ltage

(V

)

1.2

0.6

0Input

Output

Output

Input

Vol

tag

e (

V)

Time (ps) Time (ps)

• Fast analytical modeling and computational technique for logic SER analysis for cell level designs– Excellent accuracy compared to

SPICE– Best Paper Award, ISQED 2006

0

0.01

0.02

C1 C2 C3 C4 C5 C6 C7Benchmark Circuit

Err

or

Pro

ba

bil

ity

SPICE

FASER


Roadmap of Reliability: System Susceptibility to Soft Errors: Memory Modeling

C C

Inverter 1

Inverter 2

V1V2

Iseu

• Memory arrays much more sensitive to single event upsets

• Developed first analytical model for predicting SER noise margins under dynamic disturbances (single event upsets)

0

0.2

0.4

0.6

0.8

0 20 40 60

Tcrit (ps)

I n (

mA

)

Analyitcal

SPICE

Bounds

Isnm


Roadmap of Reliability: Synthesis for Reliability and Probabilistic Testing

• Optimize reliability usingrecent competitive synthesis frameworks– Allow or veto logic

transformations– Using ABC from Berkeley

• Probabilistic test– Take deterministic patterns– Compute multiplicities

using a reliability evaluator

• Evaluating 4 GSRC reliability evaluatorsand two more– Figure out which work !

• Use in estimation• Use in synthesis

and optimization• Use in circuit test

New project withAir Force Research Lab


Roadmap of Power and Variability: Energy-Optimal Gate Sizing for Subthreshold Circuits

• Subthreshold energy efficiency is limited by leakage– Energy optimal supply voltage, Vmin, determined by rise in leakage– At Vmin, leakage accounts for ~30% of total energy

• Increasing gate sizes along critical paths can reduce energy– Shorter clock period = shorter leakage time– A reduction in leakage affects the location of Vmin; therefore, Vdd can

be reduced if leakage is reduced

• An energy-driven, TILOS-like sizing algorithm yields energy savings of ~6-15% on ISCAS85 benchmarks

E Edyn E leak CVdd2 Ileak Vdd TCLK

0.0 0.2 0.4 0.6 0.8 1.00

100

200

300

400

BeforeAfter

Nu

mb

er o

f P

ath

s

Delay (Normalized to TCLK

)

0.0 0.2 0.4 0.6 0.8 1.00

100

200

300

400

500

600

700Before After

c499

c7552

Nu

mb

er o

f P

ath

s

0.0 0.2 0.4 0.6 0.8 1.00

100

200

300

400

BeforeAfter

Nu

mb

er o

f P

ath

s


)

0.0 0.2 0.4 0.6 0.8 1.00

100

200

300

400

500

600

700Before After

c499

c7552

Nu

mb

er o

f P

ath

s

0.0 0.2 0.4 0.6 0.8 1.00

100

200

300

400

BeforeAfter

Nu

mb

er o

f P

ath

s


)

0.0 0.2 0.4 0.6 0.8 1.00

100

200

300

400

500

600

700Before After

c499

c7552

Nu

mb

er o

f P

ath

s

6% energy reduction

15% energy reduction


Roadmap of Power and Variability: Design Assessment under Realistically Available Uncertainty Descriptions

• In practice, detailed process characterization data for current and future generations are not available– Only partial probabilistic descriptions

are accessible, e.g., mean and variance

– Timing, power, and parametric yield estimates are affected

• Probabilistically-enhanced interval analysis– Use mean, variance, and intervals

of circuit parameters to estimate probabilistic bounds for timing and power

– Probability box: bounds for cumulative distribution function -0.10 -0.08 -0.06 -0.04 -0.02 0.00

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Cu

mu

lati

ve

Pro

ba

bil

ity

Vdd (V)

X X

[ ]E X [ ]Var X


Roadmap of Power and Variability: Intra-Gate Biasing

• Exploit edge effects in modern MOSFET devices that lead to different Ion/Ioff current densities based on position in channel

• Key: lengthen channel near edges to suppress high leakage there, reduce Ldrawn in center slightly to compensate

• FREE circuit-level leakage reduction on the order of 5-6%– No delay penalty or optimization cost

• An orthogonal knob to all other circuit optimization techniques

200 400 600 800 10002

4

6

8

10

12

14

Leak

age

Impr

ovem

ent (

%)

Width (nm)

Leakage Improvement vs Width


Roadmap of Cost: Low-Volume Implementation

• What can be recovered along cost trajectory of Moore’s Law?– OPC, reticle plan, multi-layer reticle strategy, multi-flow production strategy,

wafer shot map, blading, mask write and inspect, dicing plan, … many optimization opportunities

– Goal: 10X reduction in per-die cost for low volume


MFMLMP Reticles

• A reticle has multi-layers of multi-projects of multi-flows• Different printing frames for different wafers• More design challenges: layer assignment, flow embedding and

frame floorplan

Die 1Lay 3

Die 2Lay 3

Die 1Lay 2

Die 2Lay 2

Die 1Lay 1

Die 2Lay 1

Reticle 1

Reticle 2Wafer 1

Die 1 Die 2 Die 1 Die 2

Wafer 2

Die 1Lay 2

Die 1Lay 1

Die 1Lay 3

Die 2Lay 1

Die 2Lay 3

Die 1Lay 1

Die 1Lay 3

Die 2Lay 2

Die 2Lay 1

Die 2Lay 3

Example of MFMLMP Reticles: Layer 2 of Die 1 and Die 2 cannot share the same reticle

Frame


GSRC On-Line MFMLMPR Designer

• Flexible: Handles all known practical design constraints• Fast: Interactive solver to minimize manufacturing costs• Graphical viewing of output• Co-developed with, used at Cypress Semiconductor for MFMLMP Reticle design

Define Parameters Input Data Output


Roadmap for Physical Implementation QOR

• Delay, Power: large part in interconnect– Growing problem with every technology node– Spatial embedding becomes more critical– Unpleasant surprises at first spatial

embedding(industry: many RTL designs are found infeasible)

• Early planning for distances, shapes and sizes– Manual planning has hit the complexity limit– System must co-evolve with its spatial

embedding– Embedded memories, IPs, analog/RF, …

• Vertically-consistent spatial embedding– Consistent objectives and optimizations

through multiple levels of abstraction– Smooth transitions between design steps,

with gradual refinement– Support for design optimizations such as

high-level and RTL synthesis


Vertical Consistency (1)

• SCAMPI: SCalable Advanced Macro Placement Improvements

– Variety of macro sizes & shapes– Look-ahead, macro clustering,

obstacle evasion• Floorist:

Floorplan Assistant(constraint-driven FP repair)

red: overlap

blue: block movement(no overlap)


• Physically safe logic restructuring• Top-down whitespace & buffer area allocation

• Support for design optimizationsvia selective re-embedding (below)

• More direct optimization of routed net lengths (ROOSTER), at several design steps

Legalize

Improve

Vertical Consistency (2)


SLLR Theme Posters• Parametric Yield Estimation and Optimization

– Eric Karl, Dennis Sylvester and David Blaauw: Multi-Mechanism Reliability Modeling and Management in Dynamic Microprocessor-Based Systems

– Scott Hanson, Dennis Sylvester and David Blaauw: A New Technique For Jointly Optimizing Gate Sizing and Supply Voltage in Ultra-Low Energy Circuits

– Saumil Shah, Dennis Sylvester, Andrew Kahng and Youngmin Kim: Intra-Gate Channel Length Biasing for Transistor-Level Circuit Optimization

• Roadmap of Reliability– Bin Zhang and Michael Orshansky: Evaluating Reliability of On-Chip SRAM Arrays using Dynamic

Stability Analysis – Rajeev Rao, Vivek Joshi, David Blaauw and Dennis Sylvester: Efficient Soft Error Rate

Computation and Circuit Optimization Techniques to Mitigate Soft Errors in Combinational Logic– Wei-Shen Wang and Michael Orshansky: Yield Estimation under Realistic Descriptions of

Parameter Uncertainty • Roadmap of Cost

– Andrew Kahng and Xu Xu: A General Framework for Multi-Flow Multi-Layer Multi-Project Reticle Design

• Roadmap of Physical Implementation QOR– Jarrod Roy and Igor Markov: Vertically-Consistent Spatial Embedding of Integrated Circuits and

Systems• Roadmap of Power and Variability

– Andrew Kahng, Swamy Muddu and Chul-Hong Park: A Scalable Auxiliary Pattern-Based OPC Strategy for Better Printability, Timing and Leakage Control

– Andrew Kahng and Swamy Muddu: Design-Centric Modeling and Optimization of BEOL Interconnect Stacks

– Andrew Kahng, Kambiz Samadi and Puneet Sharma: Study of Floating Fill on Interconnect Capacitance

– Andrew Kahng and Kambiz Samadi: Nanometer Era CMP Fill for Variability Reduction– Andrew Kahng and Puneet Sharma: CMP Fill for Reduced STI Variability– Andrew Kahng and Swamy Muddu: Predictive Modeling of Systematic Intra-die Variability– Andrew Kahng and Rasit Topaloglu: Interconnect Optimization through Design Rule Generation


Toward System Scaling TheoryTraditional Scaling

• Driven by min feature size

• Determinism: size directly impacts performance and density

• FO4-based performance metric

• Transistors are either logic or memory

• Cost not discussed (e.g., design TAT, leakage current from Tox scaling, …)

Future Scaling• Driven by system constraints

• Non-determinism: size impact mediated by power density, redundancy overhead, low yield, increased comm overhead

• System-level overdesign and effective transistor density

• Performance is achieved by multi-core architectures running at lower frequencies• Adaptivity/reliability many transistors are used to diagnose and tune• Power trades off with design time• Impacts of concurrency, spatial embedding, application domain, …


Future: GSRC Modeling and Metrics SIG

• Enable system design to comprehend impact and feasibility of technology options– Variability, power, cost– Reliability, flexibility, resilience

• Initial focus: uncalibrated, “variational” scaling models– Priority: modeling requests from system-level design and GSRC sponsors– “X% increase in reliability requires Y% increase in power”?– “X% (transient + hard) fault coverage can be achieved with < Y% area overhead”?– How to measure efficiency and yield in the presence of failures?– Approximations + Abstractions “block models” for system optimization

• Future system scaling is dominated by silicon non-idealities– Variability and reliability will fundamentally change density, power, speed, cost scaling laws– Long-term goal: a new system scaling theory

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GSRC Annual Symposium September 28 & 29, 2006 Faculty: Kahng, Markov, Orshansky, Sylvester GSRC...

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