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CSCE 612: VLSI System Design
Instructor: Jason D. Bakos
VLSI Design
• What is VLSI?
– “Very Large Scale Integration”
– Defines integration level
– 1980s hold-over from outdated taxonomy for integration levels
• Obviously influenced from frequency bands, i.e. HF, VHF, UHF
– Sources disagree on what is measured (gates or transistors?)
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SSI – Small-Scale Integration (0-102)
MSI – Medium-Scale Integration (102-103)
LSI – Large-Scale Integration (103-105)
VLSI – Very Large-Scale Integration (105-107)
ULSI – Ultra Large-Scale Integration (>=107)
VLSI System Design 2
Integration Level Trends
Obligatory historical Moore’s law plot
VLSI System Design 3
Integrated Circuits/MEMs
• Today, VLSI refers to systems impl. w/integrated circuits
– Integrated circuit refers mostly to general manufacturing
technique
• micro/nano-scale devices on a semiconductor (crystalline) substrate
• Formed using chemical/lithography processing
• What kind of devices / structures?
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transistors (bipolar, MOSFET)
wires (interconnects and passives)
diodes (junction, LEDs, VCSELs, MSM, photoconductor, PiN)
MEMs (piezoelectric integration, accelerometers, gyroscopes,
pressure sensors, micro-mirrors)
• For CMOS digital design, we only use MOSFET transistors
(used as switches) and wires
VLSI System Design 4
Chips
• Integrated circuits consist of:
– A small square or rectangular “die”, < 1mm thick
• Small die: 1.5 mm x 1.5 mm => 2.25 mm2
• Large die: 15 mm x 15 mm => 225 mm2
– Larger die sizes mean:
• More logic, memory
• Less volume
• Less yield
– Dies are made from silicon (substrate)
• Substrate provides mechanical support and electrical common
point
VLSI System Design 5
VLSI Design
• Draw polygons that represent layers deposited on the
substrate
– More of an art than science
Scale:
approximately
10 um x 10 um
• One 2-input NAND gate with 4 transistors
• Typical microprocessor contains 50 – 200 million transistors
(10-50 million gates)
VLSI System Design 6
VLSI Design
• Manual layout design is obviously not practical
• Design complexity:
– Manually drawing layout for a billion transistors would take too long
– Even if we could…
• How to verify (test) designs for functionality, speed, power, etc.?
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Complexity scales faster than actual design
• How to reuse designs?
• How to create human-readable designs?
• How to speed-up design process?
• These problems form a great deal of work
– Electronic Design Automation (EDA)
– a.k.a. CAD
• Advancing EDA technology, physical fabrication technology,
advanced designs, and IP form bulk of work (and money) in VLSI
VLSI System Design 7
EDA Tools
• Conclusion:
– This course is about using design tools to manage design
complexity of VLSI systems
– Only way to learn tools: practice and work with tools
individually
– Must teach IC fundamentals, but prevent course from
becoming semiconductor theory, analog electronics, circuits, or
digital logic course
• Target large-scale integration and EDA
• Reach good balance between fundamental IC theory and automated largescale design methodology
• 80-90% of course time will be spent in lab
– Tutorials will provide basic knowledge
– Must learn the tools on your own (assisted by instructor)
VLSI System Design 8
Course Overview
• This course is called “VLSI System Design”
• Focus on large-scale system design (CAD tools)
• CAD tools manage design and verification complexity
• What we have…
– Latest, most advanced CAD tools in the EDA industry
– Three primary players
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Synopsys, #258 ($1.2 billion revenue)
Cadence Design Systems, #259 ($1.1 billion revenue)
Mentor Graphics, ?
Comparison: Microsoft #95 ($36.8 billion), Intel #102 ($34.2 billion)
– Fabrication award for 500 nm CMOS fabrication process
• AMI C5N process with academic design kit (NCSU CDK)
• 1.5 mm x 1.5 mm die size, multiple dies, packaging
VLSI System Design 9
EDA Tools
• Big companies, lots of money, 40 years of integrated circuit
design experience, conferences, journals, powerful PCs…
what’s the problem?
• IC CAD tools are difficult to use
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Written by electrical engineers (not professional programmers)
Incredibly buggy
Not documented
Rely on ancient, outdated file formats for interoperability
Still mostly rely on command-line interfaces
Utilize outdated, primitive, buggy APIs for GUIs
Inherently required to solve hard problems
• Place components, route wires
• Must utilize advanced heuristics that are only as good as fabrication process
technology information and user input (garbage-in, garbage-out)
VLSI System Design 10
EDA Tools
• Cadence tools
– “IC-Tools” => IC5141 package (Linux)
– Collection of tools managed by Design Framework II (dfII)
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Virtuoso schematic/layout editor
Analog Environment
Spectre simulator
Diva DRC, EXT, LVS
• Other Cadence tools
– SignalStorm => TSI42 package (Linux)
– Abstract Generator => DSMSE54 (Solaris)
– First Encounter => SOC42 package (Linux)
• Synopsys
– Design Compiler (Linux)
• Mentor
– HDL Designer (Linux)
VLSI System Design 11
What EDA Tools Can Do
• Manual layout vs. EDA is like:
– Manual transmission vs. automatic transmission
– HTML programming vs. Frontpage
– Assembly code programming vs. compiled high-level language
• Manual layout for small, optimized designs will always be
superior
• EDA techniques for larger-scale designs will always be
superior (verification, reusability, NRE, etc.)
• Goal: do careful, manual design of smaller components
(cells) and use EDA to combine them for large-scale design
VLSI System Design 12
What EDA Tools Can Do
• “My” Design Flow
Abstract Generation
Circuit Sim
Digital cell library
design
process
info, cell
abstracts
Cadence AbGen
Cadence IC-Tools
Characterization
Cadence IC-Tools
char. info
Cadence SignalStorm
Design
Specification
Standard Cell Library
Behavioral VHDL
Design
Mentor HDL Designer
Synthesis
VHDL
Synopsys Design
Analyzer
Behavioral Simulation
Cell Timing Simulation
Mentor ModelSim
Mentor ModelSim
Place-and-Route
Verilog
Cadence First
Encounter
Interconnect Timing
Simulation
Mentor ModelSim
VLSI System Design 13
Course Organization
• Course will be divided into
units
– Introduction: IC design
and fabrication
fundamentals
• Lectures
• Assignments from textbook
– CMOS circuit design,
layout, and simulation
• Tutorial: Cadence IC-Tools
• Design projects
• Development of standard cell
library
– Cell library development
• Tutorial: Cadence SignalStorm
and Abstract Generator
• Report on cell library
– VHDL Design
• Lectures on VHDL
• Tutorial: Mentor HDL
Designer
• Design project
– Logic Synthesis
• Tutorial: Synopsys Design
Analyzer
– Place-and-route
• Tutorial: Cadence First
Encounter
– Course project
• Teams?
• Design?
• Fabrication?
VLSI System Design 14