CGRA QUIZ. Quiz What is the fundamental drawback of fine-grained architecture that led to exploration of coarse grained reconfigurable architectures?

CGRA QUIZ

Quiz• What is the fundamental drawback of fine-grained

architecture that led to exploration of coarse grained reconfigurable architectures? (Max of 5 words!)

• Give two examples for each coarse grained architecture type: Mesh, Linear Array, and Crossbar

• Indicate whether the given architecture supports some form of partial reconfiguration or not.

PipeRanch, KressArray, Chess

COARSE GRAINED RECONFIGURABLE ARCHITECTURES

04/21/2014

Aditi Sharma

Dhiraj Chaudhary

Pruthvi Gowda

Rachana Raj Sunku

DAY - 2

3

Outline• Coarse Grained Reconfigurable Architectures

• RAW• CHESS

• Basics Of Network On Chip(NoC)

• Project Overview

4

Raw Architecture Workstation (RAW)

• Developed at MIT• It fully exposes Low Level

hardware architectural details to the compiler

• It lacks hardware for register renaming and dynamic instruction issue

• A Raw architecture seeks to execute pipelined application (like signal processing) efficiently. Motivation ???

Waingold, Elliot, et al. "Baring it all to software: Raw machines." Computer 30.9 (1997): 86-93.

5

Change Is Around the Corner

• Processor performance not scaling as before• Wire delay and power

old view: chip looks small to a wire

chip size

distance signal can travelin 1 cycle

new view: chip looks much bigger to a wire,communication is expensive even on chip!


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Raw Architecture

How do we arrive at this design???


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Problems with Monolithic Designs• Super-wide general purpose processors are no longer

practical

WideFetch(16 inst)

UnifiedLoad/StoreQueue

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LUBypass Net

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• Centralized control with global operand routing

• Area, power, and frequency concerns


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WideFetch(16 inst)


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Spatial Architectures


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Exploiting Locality


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Distribute the Register File


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Control

WideFetch(16 inst)


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Tiled-Processor Architecture


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Tiled-Processor Architecture

• Make a tile as big as you can go in one clock cycle, and expose longer communication to the programmer


• Tile abstraction is quite powerful– e.g., power → resources

used as necessary

• Easily scalable• All signals registered at tile

boundaries, no global signals• Easier to Tune the

Frequency• Easier to do the Physical

Design• Easier to Verify

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Raw On-Chip Networks• 2 Static Networks

• Provides low latency communication between tiles.

• Makes routing decision during compile time.

• 2 Dynamic Networks• Header encodes destination.• Transports unpredictable

operations like interrupt and cache misses.

ComputationResources

SwitchProcessor


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Inside the Compute Processor

IF RFDA TL

M1 M2

F P

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F4 WB

r26

r27

r25

r24

InputFIFOsfromStaticRouter

r26

r27

r25

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OutputFIFOstoStaticRouter

Local BypassNetwork

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Raw Compiler Example

tmp3 = (seed*6+2)/3v2 = (tmp1 - tmp3)*5v1 = (tmp1 + tmp2)*3v0 = tmp0 - v1….

pval5=seed.0*6.0

pval4=pval5+2.0

tmp3.6=pval4/3.0

tmp3=tmp3.6

v3.10=tmp3.6-v2.7

v3=v3.10

v2.4=v2

pval3=seed.o*v2.4

tmp2.5=pval3+2.0

tmp2=tmp2.5

pval6=tmp1.3-tmp2.5

v2.7=pval6*5.0

v2=v2.7

seed.0=seed

pval1=seed.0*3.0

pval0=pval1+2.0

tmp0.1=pval0/2.0

tmp0=tmp0.1

v1.2=v1

pval2=seed.0*v1.2

tmp1.3=pval2+2.0

tmp1=tmp1.3

pval7=tmp1.3+tmp2.5

v1.8=pval7*3.0

v1=v1.8

v0.9=tmp0.1-v1.8

v0=v0.9

pval5=seed.0*6.0

pval4=pval5+2.0

tmp3.6=pval4/3.0

tmp3=tmp3.6

v3.10=tmp3.6-v2.7

v3=v3.10

v2.4=v2

pval3=seed.o*v2.4

tmp2.5=pval3+2.0

tmp2=tmp2.5

pval6=tmp1.3-tmp2.5

v2.7=pval6*5.0

v2=v2.7

seed.0=seed

pval1=seed.0*3.0

pval0=pval1+2.0

tmp0.1=pval0/2.0

tmp0=tmp0.1

v1.2=v1

pval2=seed.0*v1.2

tmp1.3=pval2+2.0

tmp1=tmp1.3

pval7=tmp1.3+tmp2.5

v1.8=pval7*3.0

v1=v1.8v0.9=tmp0.1-v1.8

v0=v0.9

Assign instructions to the tiles, maximizing locality. Generate the static routerinstructions to transferOperands & streams tiles.

[Slide Source: Michael B. Taylor]

Raw tile

Architectural Comparison

RAW Superscalar Multiprocessor


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Application Mapping on RAW

[

Four-way parallelized scalar code

Two-way threaded Java program

httpd Zzzz..

VideoData Stream

Frame BufferAnd Screen

Custom Data Path Pipeline(by Compiler)

Sleep Mode (power saving)Fast Inter-tile ALU

forwarding : 3 cycles


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RAW - Performance

Taylor, Michael Bedford, et al. "Evaluation of the Raw microprocessor: An exposed-wire-delay architecture for ILP and streams." ACM SIGARCH Computer Architecture News. Vol. 32. No. 2. IEEE Computer Society, 2004.

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CHESS - A Reconfigurable Arithmetic Array For Multimedia Applications • Designed by Hewlett Packard laboratories in the year

1999• Aims at speeding up arithmetic operations for multimedia

applications and tries to improve memory density• Principle goals of CHESS

• Increased arithmetic computational density• Increased memory bandwidth• Increased capacity of internal memories• Enhanced Flexibility• Rapid Reconfiguration

24

Marshall, Alan, et al. "A reconfigurable arithmetic array for multimedia applications."

CHESS - Architecture• 4 bit ALUs• 4 bit bus wiring• Switchboxes• Chessboard Layout• Embedded block RAM’s• Speed and hierarchical line lengths• Small configuration memories• No run-time reconfiguration

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CHESS - ComponentsALU LOGIC DESIGN

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Switchbox


CHESS - Routing Structure

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CHESS - Performance

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• High computational density• Efficient multiplies due to embedded

ALU

• Issues: • No reported software or application

results• No run-time reconfiguration


Comparison: CHESS and MATRIX• Both use 2D array of ALUs• For both, instructions can be generated within the array• Both the architectures are flexible• CHESS is 4 bit whereas MATRIX is 8 bit• CHESS does not support run-time reconfiguration but has

very fast configuration as few bits are required• CHESS has high computational density• CHESS is aimed at arithmetic operations whereas

MATRIX is more general purpose

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Network-On-Chip(NoC)

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Project Overview• Implementing Coarse Grained and Hybrid Reconfigurable Architecture • NoC interconnection between processing elements• Supports Variable Block Size Motion Estimation• Motion Estimation Algorithms

• Full Search• Diamond Search

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Verma, Ruchika, and Ali Akoglu. "A coarse grained and hybrid reconfigurable architecture with flexible NoC router for variable block size motion estimation." Parallel and Distributed Processing, 2008. IPDPS 2008. IEEE International Symposium on. IEEE, 2008.

CPE(1,1)CPE(1,1)

CPE(2,1)CPE(2,1)

CPE(3,1)CPE(3,1)

CPE(4,1)CPE(4,1)

CPE(1,2)CPE(1,2)

CPE(2,2)CPE(2,2)

CPE(3,2)CPE(3,2)

CPE(4,2)CPE(4,2)

CPE(1,3)CPE(1,3)

CPE(2,3)CPE(2,3)

CPE(3,3)CPE(3,3)

CPE(4,3)CPE(4,3)

CPE(1,4)CPE(1,4)

CPE(2,4)CPE(2,4)

CPE(3,4)CPE(3,4)

CPE(4,4)CPE(4,4)

c_d

c_d

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r_d

r_d

r_d

r_d

c_d

c_d

c_d

c_d

r_d

r_d

r_d

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c_d

c_d

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r_d

r_d

r_d

r_d

r_d

r_d

r_d

r_d

c_d

c_d

c_d

c_d

PE 2(1)PE 2(1)

PE 2(3)PE 2(3)

PE 2(2)PE 2(2)

PE 2(4)PE 2(4)

PE 3PE 3

Main MemoryMain Memory Memory Interface (MI)Memory Interface (MI)

data_load_control

(16 bits)

reference_block_id (5 bits)

c_d_(x,y)

(32 bits)

r_d_(x,y)

(32 bits)

32 bits

14 bits

12 bits

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QUESTIONS??

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Documents

CGRA QUIZ. Quiz What is the fundamental drawback of fine-grained architecture that led to exploration of coarse grained reconfigurable architectures?