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Introduction to Integrated Systems Design Automation Outline Why Do You Care? Technology Trends Process and Device Technology Logic Technology Memory Technology.

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Presentation on theme: "Introduction to Integrated Systems Design Automation Outline Why Do You Care? Technology Trends Process and Device Technology Logic Technology Memory Technology."— Presentation transcript:

1 Introduction to Integrated Systems Design Automation Outline Why Do You Care? Technology Trends Process and Device Technology Logic Technology Memory Technology Packaging Technology Effect on Processor Design Hank Walker

2 Why Do You Care About Technology? IC design is often technology driven try building a 1 GHz, low-power uP with vacuum tubes designers say what they need but technologists tell them what they get Competitive designs must balance utility and cost use available technology to balance: - speed - standards - weight - form factor - power consumption - now the most critical issue - reliability - cost You usually have to shove 10 lb. into a 5 lb. bag

3 Good Technology Trends More Transistors at Lower Cost bigger chips - at introduction smaller geometries ~250M transistors common in 2005 Higher Speed faster transistors shorter distances Smaller Size and Weight higher packing densities packaging advances Merger of IC and Packaging Technology chip is the package

4 Bad Technology Trends Abstractions Break Down must “listen to the silicon” to achieve optimal designs concurrent circuit-layout-device design concurrent electrical-packaging design technology-dependent architectural, RTL, logic design => except when design is simple and slow and boring Law of Large Numbers Stops Working number of atoms now matters transistors don’t shut off - lots of wasted leakage power you've got to remember your quantum mechanics Diverging Requirements desktop - high speed, low cost, power limits portable - low power, low weight, small size, low voltage, low cost embedded - low cost, harsh environment, high reliability

5 Process Technology Geometries lateral: ~65 nm today, ~4 nm demonstrated vertical: ~15 nm today, ~ 3 atoms demonstrated shrinking ~15%/year limited by deposition, etch, implant, lithography equipment limited by $$$ - new fab cost $3B+ Die Size (big chips) ~2 cm 2 at introduction, ~1 cm 2 in volume growing ~20%/year limited by yield => ~2x transistors/chip every 1.5 years

6 System on a Chip (SoC) 2005 Blade server Volume Intro

7 Process Technology Interconnect TiN, poly, 8-9 layers of copper more metal layers in future minimum resistance - copper is it, silver no good lower capacitance - low-K dielectrics on-chip transmission lines - controlled impedance - crosstalk elimination optical waveguides? superconductors don’t help much - still LC Interconnect delays not scaling with technology

8 Device Technology Current CMOS - strained Si channel - elevated source/drain soon BiCMOS - CMOS + NPN, maybe PNP thin-film MOS transistors - replace resistors as SRAM pullups - LCD displays GaAs MESFETs -RF, high temperature applications SiGE BJTs, MOSFETs -RF Future 3D devices - FinFET, trigate field oxide metal field oxide metal

9 Systems are Getting Faster Must scale V TH and V DD to increase speed –Causes more leakage –P4 leaks ~20A, ~1/3 of its power!

10 Motorola BiCMOS Technology 100 ps ECL gate delay 0.5 µ m channel length 3 layer metal silicides dual well Still used in RF, high power circuits

11 Process and Device Issues BJT, MOSFET R.I.P.? fundamental limits reached in ~10 years - but it has always been ~10 years away delay some by going vertical Supply voltage -> 0V limit electric fields reduce hot carriers Increased variability number of atoms in a region is now countable Technology CAD process and device simulation a key limit to progress Growing fabrication line cost $3B+ for new Intel fabs

12 Logic Technology Bipolar/BiCMOS –Still used for analog circuits –Fewer circuit compromises –Does not scale well –Still excellent for high power, high voltage CMOS –Used for all logic –Used for most analog due to lower cost –Now increasing RF usage »TI one-chip cell phone Z Z

13 Logic Technology Design Styles standard cells - library of functions sea of gates - big bag of gates, routing on top full custom - very high volume only mixed custom/semi-custom – on all large chips mixed analog/digital - common in consumer products Trends time-to-market dominates over manufacturing cost - product life of 1-2 years increasing percentage of designs are ASIC/FPGA - maybe volume too semicustom logic surrounding standard core -e.g µ P with custom I/O interfaces -Xilinx Virtex II Pro – PowerPC on FPGA

14 Memory Density –2x every 1.5 years Cost –Declines 30%/year – most important metric SRAM –Usually mixed with logic on same chip EEPROM (flash) –Lower programming voltages for integration with logic –Scaling problems ROM –Declining importance –Time to market, field programmability

15 Memory I/O asynchronous => synchronous memory-interface bus => memory-CPU bus - DDR, RAMBUS Increasing Specialization VRAM cache RAM mixed DRAM/SRAM synchronous DRAM

16 Memory Issues Density Limits traditional DRAM beyond ~Gb unlikely electric fields radiation delayed some with deep trenches, new dielectrics already close to area of two wires crossing MRAM – SRAM w/magnet DRAM speed lagging logic - Must amplify small charge - More bits => longer I/O path - Higher speed => higher cost, lower density

17 Memory vs. Logic Speed

18 Packaging Power distribute power with low IR drop constant power, lower supply voltage => higher current large numbers of pins to supply current – 1000s of pins Signal Delay and Integrity controlled impedance to control delays shielding to reduce cross-talk => transmission lines I/Os Rent's Rule: I/O count ~ 64-bit addr, 64-bit data, instr and data caches => 256 pins TAB or flip-chip on glass for flat panel displays

19 Packaging Cooling fin tower and low-speed fan near its limit - ~130W for P4, check heat sinks on Apple desktop higher fan speed too noisy for office environment => air impingement – manifolds in current PCs => heat pipe to larger heat sink – some laptops chilled air - requires A/C in cabinet liquid impingement - plumbing, big package => liquid microchannels - small, low flow, W/cm 2 ! portables limited to conduction, some natural convection LAPTOP TOO HOT FOR YOUR LAP! Size, Weight eliminate pins eliminate package - glop of epoxy covering chip

20 Packaging Multi-Chip Modules (MCMs) IC processing to pattern interconnect layers on substrate Put L3 cache close to processor Pin Grid Arrays (PGAs) fallen from favor - area, lead length Leadless Chip Carriers (LCCs) continues as mainline solution multiple rows to increase pinouts without area increase Dual In-line Package (DIP) only for small chips

21 Exotica Process and Device HEMT (high electron mobility transistor) high Tc superconductors - interconnect and devices quantum well devices (particle in a box) Packaging LN2 cooling - 2x speed improvement with optimized process - small geometry devices require it to work - refrigeration is expensive, noisy, unreliable - thermoelectric cooling might be solution wafer scale integration - system on monolithic substrate - Cost competition w/regular ICs May see specialized use over next 10 years

22 Effect on Architectural Design Problems isochronic regions shrinking rapidly - speed < c, it's the law takes multiple clock cycles to go across chip global knowledge is expensive, or stale memory speeds not keeping up with logic speeds -A return to the bad old days of core? -Do memory fetch, then go get a cup of coffee portable systems - maybe no power or disk Solutions small memories close to logic – cache hierarchy loosely coupled components – multiple cores on a chip yesterday's supercomputer problems in today’s desktops (flash) EEPROM for nonvolatile programmability w/o battery or disk

23 Effect on Logic Design Problems delays across packages and boards limited I/O count power dissipation balance clocking Solutions simultaneous partitioning across package levels more knowledge of circuit-layout-package iterate if necessary - possible with automatic synthesis self-timed logic?

24 Effect on Circuit Design More device options bipolar, CMOS, thin-film devices optimized for both logic and memory Everything is sort of analog I-V curves and logic transitions degrade more current-mode operation Device variability increases simpler circuits fewer matched timing chains => must use physically-based statistical design => self-timed logic? More complex simulation mixed circuit/device interconnect parasitics => use characterized cell library as much as possible

25 Effect on Layout Design Global routing critical to performance simultaneous place and route Delay and Crosstalk Control selective use of on-chip transmission lines 2.5D => 3D topology complex design rules parasitic extraction tight loop back to circuit design

26 Effect on Package Design Packaging as important to uPs as supercomputers system cost system performance system weight system form factor environmental limitations Can't throw design over wall to MechEs concurrent package and electrical design constraints of packaging on electrical design electrical and thermal behavior of packaging on circuit - within package as well as on MCM or board => ECEs must learn some ME package dominates in portables

27 Bad Market Trends Competitive pressure –decreasing time to market –decreasing market window –falling system price Result –build more complex systems in less time with fewer people –shove 10 lb into a 5 lb bag Time to Market Time System Price

28 The Problem Electronic systems are most complex artifacts built –~1B transistors in dual-core Itanium –~25M transistors in Power4 CPU core – now a “commodity” We’re only human –best humans can design 10s of transistors per day by hand –1000 person-years for original Pentium –$100M design cost (~$200M in today’s dollars) –2-3 year design time => designers - barely doable –cannot keep on that trend Product failure == corporate death –IC fab cost $3B in 2003 (TI Richardson fab) »$493k/day 6% interest rate –chip-in-product sales >$20M/day –delay == death

29 Conclusion Design automation is crucial for economic survival Design automation must: –improve our productivity faster than technology curve –achieve greater optimality –achieve higher-quality results –handle additional physical effects –and do it all on larger designs DA tools are primary limiting factor in IC design –a race between EDA and technology –“solving yesterday’s problem tomorrow” - Mark Pinto

30 EDA Tools Product-Level Design synthesis across boards and chips multi-level optimization focus on meeting user-level specs humans mostly out of tool loop Product engineers are primary tool users other engineers act as consultants tool users and developers in same location Design for Manufacturability/Profitability CAD tools will know manufacturing process statistical design merger of design and manufacturing engineering

31 Two Visions of Computer Design* 1. Team of design experts aided by CAD tool gurus. - gurus fix tools when they break 2. Team of CAD tool gurus aided by design experts. - experts supply knowledge tools don't have * Dave Ditzel, then at Sun

32 Homework Skim the Semiconductor Industry Association International Technology Roadmap for Semiconductors (ITRS) The industry consensus on technology needs to stay on technology trends Read chapters on design and test


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