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Design ITWG ITRS-2001 Grenoble Meeting April 27, 2001.

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Presentation on theme: "Design ITWG ITRS-2001 Grenoble Meeting April 27, 2001."— Presentation transcript:

1 Design ITWG ITRS-2001 Grenoble Meeting April 27, 2001

2 Roadmap for basic analog / RF circuits Mixed-Signal Roadmap Figures of merit for four important basic analog building blocks are defined and estimated for future circuit design From these figures of merit, related future device parameter needs are estimated (PIDS table, owned by Design) and feedback is given Roadmap for device parameters (needs) A/D-Converter Low-Noise Amplifier Voltage-Controlled Oscillator Power Amplifier L min 2001 … 2015 …… analog transistor g m /g ds ……

3 SOC Low Power Scenario Low Power Constant-power scenario: slower clock, fewer Tr, lower Vdd, …

4 New MPU Clock Model Global clock: flat at 14 FO4 INV delays –FO4 INV delay = delay of an inverter driving a load equal to 4 times its input capacitance –no local interconnect: negligible, scales with device performance –no (buffered) global interconnect: (1) was unrealistically fast in Fisher98 (ITRS99) model, and (2) global interconnects are pipelined (clock frequency is set by time needed to complete local computation loops, not time for global communication - cf. Pentium-4 and Alpha-21264) Local clock: flat at 6 FO4 INV delays –somewhat meaningless: only for ser-par conversion, small iterative structures, marketing interpretation of phase-pipelining –reasonable alternative is to delete from Roadmap ASIC/SOC: flat at FO4 INV delays –absence of interconnect component justified by same pipelining argument, and by convergence of ASIC / structured-custom design methodologies, tools sets –higher ASIC/SOC frequencies possible, but represent tradeoffs with design cost, power, other figures of merit –low information content reasonable alternative is to delete from Roadmap

5 Layout Density Models (A Factors) Semi-custom Logic: Avg size of 4t gate = 32MP 2 = 320F 2 –MP is contacted lower-level metal pitch –32 = std-cell height 8 tracks by width 4 tracks (avg NAND2) –whitespace factor; overall model scales quadratically Custom Logic: 1.25x ASIC density SRAM: used in MPU: A factor decreases with scaling; still evaluating –may see paradigm shifts in architecture/stacking; eDRAM, 1-T SRAM, … –peripheral overhead %; more exact model of form K*log(A)*B A-Factor = F SRAM Cell Area (F 2 )

6 Power Constraint Implications: Logic - Memory Balance Constant power or power density decreasing logic content #Tr Logic, SRAM wont scale together as in current ITRS Anomaly going from 45nm to 32nm due to constant Vdd

7 Design Cost and Quality Requirement Design cost of largest ASIC rises despite major DT innovations Other Dataquest numbers confirm memory content rising We are developing metric, data, requirements for design quality

8 SYSTEM DRIVERS Chapter Defines segments of silicon market that drive process and design technology Along with ORTCs, serves as glue for ITRS 4 Drivers: SOC (Japan), MPU (USA), DRAM (Korea), M/S (Europe) –SOC: driven by cost, power, integration –SOC: drives device requirements, packaging, I/O counts, … –SOC: same as ASIC-LP Each section Nature, evolution, formal definition of this driver What market forces apply to this driver ? For what technology elements (process, device, design) is this a driver ? Key figures of merit, and futures Participation of other ITWGs

9 DESIGN Chapter Context –Scope of Design Technology –High-level summary of complexities (at level of issues) –Cost, productivity, quality, and other metrics of Design Technology Overview of Needs –Driver classes and associated emphases –SOC, MPU, DRAM, MS –Resulting needs (e.g., power, …, cost-driven design) Summary of Difficult Challenges Detailed Statements of Needs, Potential Solutions –System-Level, Circuit, Logic/Physical, Verification, Test

10 Backup Slides

11 MPU Diminishing Returns Pollacks Rule –In a given process technology, new uArch takes 2-3x area of old (last generation) uArch, and provides only 40% more performance (see Slide) –Slide: process generations (x-axis) versus (1) ratio of Area of New/Old uArch, (2) ratio of Performance of New/Old (approaching 1) –Slides: SPECint, SPECfp per MHz, SPECint per Watt all decreasing rapidly Power knob running out –Speed == Power –10W/cm 2 limit for convection cooling, 50W/cm 2 limit for forced-air cooling –Large currents, large power surges on wakeup –Cf. 140A supply current, 150W total power at 1.2V Vdd for EV8 (Compaq) Speed knob running out –Historically, 2x clock frequency every process generation 1.4x from device scaling (running into t_ox, other limits?) 1.4x from fewer logic stages (from down to around 14 FO4 INV delays) –Clocks cannot be generated with period < 6-8 FO4 INV delays –Pipelining overhead (1-1.5 FO4 INV delay for pulse-mode latch, 2-3 for FF) –Around 14 FO4 INV delays is limit for clock period (L1 $ access, 64b add) Unrealistic to continue 2x frequency trend in ITRS

12 Performance Efficiency of Microarchitectures – Pollacks Rule Area (Lead / Compaction) Performance (Lead / Compaction) Technology Generation Growth (X) Note: Performance measured using SpecINT and SpecFP Implications (in the same technology) New microarchitecture ~2-3X die area of the last microarchitecture Provides X performance of the last microarchitecture We are on the Wrong Side of a Square Law Intel: Gelsinger talk ISSCC-2001

13 Decreasing SPECint/MHz

14 Decreasing SPECfp/MHz

15 Decreasing SPECfp/Watt

16 MPU Clock Frequency Trend Intel: Borkar/Parkhurst

17 MPU Clock Cycle Trend (FO4 Delays) Intel: Borkar/Parkhurst

18 Memory/Logic Power Study Setup Motivation: Is current ITRS MPU model consistent with power realities? Does it drive the right set of needs? P total = P logic + P memory = constant (say, 50W or 100W) P logic composed of dynamic and static power, calculated as densities P memory = 0.1*P density_dynamic –power density in memories is around 1/10 th that of logic Logic power density (dynamic) determined using active capacitance density (Borkar, Micro99) –dynamic power density P density_dynamic = C active * V dd 2 * f clock –f clock uses new fixed-FO4 inverter delay model (linear, not superlinear, with scale factor) –C active = 0.25nF/mm 2 at 180nm –increases with scale factor (~1.43X)

19 Memory/Logic Power Study Setup Static power model considers dual Vth values –90% of logic gates use high-Vth with I off from PIDS Table 28a/b –10% of logic gates use low-Vth with I off = 10X I off from PIDS Table 28a/b (90/10 split is from IBM and other existing dual-Vth MPUs) –Operating temp (80-100C) I off is 10X of Table 28a/b (room temp) Width of each gate determined from IBM SA-27E library –150nm technology; 2-input NAND = basic cell –performance level E: smallest footprint, next to fastest implementation W of each device ~ 4um –W eff (effective leakage width) for each gate = 4um –0.8*W eff *I off (per um) = I leak / gate (0.8 comes from avg leakage over input patterns)

20 Memory/Logic Study Setup Calculate densities, then find allowable logic component (percent of total area) to achieve constant power (or power density) –A memory + A logic = A chip –recall that A chip is flat at 157 mm 2 from , then increases by 20% every 4 years Constant power and constant power density scenarios same until 65nm node (because chip area flat until then)

21 Power as a Constraint: Implications Using same constraints, calculate #MPU cores (12Mt/core) and Mbytes SRAM allowable (again, anomaly at 32nm due to constant Vdd)

22 Design Cost Requirement Largest possible ASIC design cost model engineer cost per year increases 5% per year ($181,568 in 1990) EDA tool cost per year increases 3.9% per year ($99,301 in 1990) #Gates in largest ASIC design per ORTCs (.25M in 1990, 250M in 2005) %Logic Gates constant at 70% (see next slide) #Engineers / Million Logic Gates decreasing from 250 in 1990 to 5 in 2005 Productivity due to 7 Design Technology innovations (3.5 of which are still unavailable) : RTL methodology; In-house P&R; Tall-thin engineer; Small- block reuse; Large-block reuse; IC implementation suite; Intelligent testbench; ES-level methodology Small refinements: (1) whether 30% memory content is fixed; (2) modeling increased amount of large-block reuse (not just the ability to do large-block reuse). No discussion of other design NRE (mask cost, etc.). #Engineers per ASIC design still rising (44 in 1990 to 875 in 2005), despite assumed 50x improvement in designer productivity New Design Technology -- beyond anything currently contemplated -- is required to keep costs manageable

23 Design Cost Requirement Source: Dataquest (2001)

24 ASIC Memory Content Trends Source: Dataquest (2001)

25 Design Quality Requirement Normalized transistor quality model speed, power, density in a given technology analog vs. digital custom vs. semi-custom vs. generated first-silicon success other: simple / complex clocking, … developing quality normalization model within MARCO GSRC; VSIA, Numetrics, others pursuing similar goals Design quality: gathering evidence, will have metric, historical trend / needs table) Design quality, and quality/cost, will show red bricks?

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