Virtual Platforms for Memory

Controller Design Space

ExplorationMatthias Jung, Christian Weis, Norbert WehnUniversity of Kaiserslautern, Germany

Microelectronic

Systems Design

64B

Standard Memory System

msms

HDD/SSDDRAM

L3 shared cache 8-12MB

.

Mem

ory

Con

trolle

r: 3

Channels

L2 private cache 256KB

L1 private cache 64KB

CORE

16B

ns

SRAM

Pin limitation

due to package

Power hungry I/O transceiver

s

Bandwidth Requirements Memory Wall

512B

Microelectronic

Systems Design

3D Stacked Wide I/O DRAM

• Stacked DRAM dies

• TSV connections

• Multiple Channels

Increasing bandwidth demand

Higher available bandwidth

1 or 2Channel DDR3

Memory controllerbottleneck

New generation of Memory Controllers is required

3D stacked DRAM

MPSoC

Microelectronic

Systems Design

Design Space Exploration with Virtual Platforms• Huge design space of 3D-DRAM controller• Flexible and cycle approx. models are needed for fast

investigation• RTL simulation is too slow for system level analysis

TLM based virtual platforms with Synopsys Platform Architect Speedup of TLM models up to 377x compared to CA1

Simulating in seconds instead of hours

1 M. Jung, et al. TLM Modelling of 3D Stacked Wide I/O DRAM Subsystems, in Proc. HiPEAC Conference 2013, Berlin.

Microelectronic

Systems Design

Special TLM DRAM Protocol1

• Application specific phases with

DECLARE_EXTENDED_PHASE()

• Phases derived from DRAM commands (Jedec Wide I/O

Standard)

• DRAM commands: ACT, PRE, RD, WR, REFA …Example:

1 M. Jung, et al. TLM Modelling of 3D Stacked Wide I/O DRAM Subsystems, HiPEAC, 2013, Berlin.

Microelectronic

Systems DesignExperiments and Results

• TLM model was compared with cycle accurate SystemC implementation

• Tested with Mediabench and CHStone Benchmark traces

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de1.000 s

10.000 s

100.000 s

1000.000 s

10000.000 s

Runtimes (Log-Scale)

CA ModelTLM Model

Speedup up to two magnitudes!

1h

41m

42s

Microelectronic

Systems Design

Power Modeling of 3D-DRAM with TLM2.02

Two parts of power consumption:

1. Background Power2. Command Power

DRAM Power states accounted with TLM phases

2 M. Jung et al. Power Modelling of 3D-Stacked Memories with TLM2.0, SNUG 2013, Munich

ACT WR PRE ACT RD WR PRE

I

t

Microelectronic

Systems Design

Results (Power Simulation)

chstone-gsm

chstone-jpeg

media-jpegdecode

media-jpegencode

mediabench-mpeg2decode

0 10 20 30 40 50 60 70 80

CA SystemC

DRAMPower

TLM2.0 Model

mW

• TLM model was compared with a cycle accurate SystemC implementation and the standalone power simulator DRAMPower3

• Tested with Mediabench and CHStone Benchmark traces

Deviation max 5%

to referencemodels

3 www.drampower.info

Microelectronic

Systems Design

Current Work: Thermal Simulation

• Co-simulation with 3D-ICE Simulator3

• Traces will be generated from GEM54

• Closed Loop Control

3 http://esl.epfl.ch/3d-ice.html 4 http://www.gem5.org/

Microelectronic

Systems Design

Conclusion

• 3D stacked DRAMs are the future technology

• Virtual platform for DSE of new multi-channel Wide I/O DRAM controllers are mandatory

• DRAM specific TLM protocol was introduced(can be used for any kind of DRAM)

• Precise Power model presented

• Early checkpoint for SW implementations

• Current and Future Work: Advanced scheduling and arbitration algorithms

Microelectronic

Systems DesignThank

you!

Visit my Poster!

http://www.uni-kl.de/3d-dram