1 Farhan Mohamed Ali (W2- 1) Jigar Vora (W2-2) Sonali Kapoor (W2-3) Avni Jhunjhunwala (W2-4) Presentation 12 MAD MAC 525 26 th April, 2006 Short Final Presentation W2 Project Objective: Design a crucial part of a GPU called the Multiply Accumulate Unit (MAC) which will revolutionize graphics. Design Manager: Zack Menegakis
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1 Farhan Mohamed Ali (W2-1) Jigar Vora (W2-2) Sonali Kapoor (W2-3) Avni Jhunjhunwala (W2-4) Presentation 12 MAD MAC 525 26 th April, 2006 Short Final Presentation.
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• Fast because it avoids having ripple carry in every stage
• Enables Compact Layout
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Design Process
• Verilog-> Schematic-> Layout– Behavioral -> Structural Verilog– Transistors/gates -> Full Schematic– Gate/Component Layout -> Top Level
• Transistor Count fluctuated from 20,200 to 12,800• Major design decisions
– Decided against implementing denormal arithmetic because it would increase the complexity of the project beyond the scope of the class
– Round performed only once at the end.– Picked nPass over Tgate in the normalize shifter– Adder: variable length carry select-> Han-Carlson binary tree
adder
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VERIFICATION OF DESIGN
Verilog Simulations ( show outputs)– Overview– How/Why it works– Behavioral/Structural
Explain why we couldn’t get a high-level simulator and how we tested our verilog design.
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SCHEMATICS
• Show schematics of major blocks: adder, multiplier, and top-level
• HOW WE VERIFIED: analog simulation
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Top Level Schematic
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Multiplier Schematic
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Adder Schematic
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FLOORPLAN EVOLUTION
• Initial floorplan
• How it evolved (with animation)- why and how we changed it
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Multiplier
Align C
Reg A
Reg
BExpCalc
Reg C
Pipeline Reg Pipeline Reg
AdderLd
Zero
Pipeline Reg
NormalizeRound
Reg Y
Main Floorplan
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Floorplan
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Full Chip LayoutExponent
AlignZero
Adder
MultiplierNormalize
Round
Ovf
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Pipelining
• Initially planned 5-6 pipeline stages
• Reduced to 4 pipeline stages – made possible by implementing fast carry lookahead adders in critical path modules (adder and multiplier)
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Pipeline Reg
Pipelining Stages
MultiplierAlign
C
Reg A
Reg
BExpCalc
Reg C
Pipeline Reg Pipeline Reg
AdderLd
Zero
Pipeline Reg
NormalizeRound
Reg Y
Pipeline Reg
Overflow checker
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LAYOUT
• Final Layout
• Layout of large blocks such as multiplier, adder and normalize
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Layout Decisions
• 3 standard cell heights
• Uniform width vdd and ground rails
• Wider vdd and ground rails in power hungry modules