Introduction

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Summary

¡ Why architecture? ¡ Technology trends ¡ Cost issues

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1 Computer architecture?

¡ Computer Architecture refers to the attributes of a system visible to a programmer (that have a direct impact on the logical execution of a program)

¡ Architectural attributes: ¡ Instruction set ¡ Data type representations ¡ I/O mechanisms ¡ Memory addressing techniques

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Computer architecture (2) ?

¡ Computer organization refers to the operational units and their interconnections that realize the architectural specifications

¡ Organizational attributes: • hardware details transparent to the programmer: • control signals • interfaces between the computer and peripherals • memory technology • Often called micro-architecture

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2 Architecture vs. organization

¡ Example: ¡ Architectural issue: • Does the computer support the multiplication instruction? ¡ Organizational issue: • Is multiplication imlemented by a special multiply unit or by a add+accumulate?

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Architecture vs. organization (2)

¡ Architecture (MIPS):

Memory (Max. 4GB) Registers 32 bits 32 bits 0x00000000 R0 0x00000004 Instruction Formats R1 0x00000008 op rs rt rdshamtfunct R2 0x0000000C 0x00000010 op rs rt offset 0x00000014 R30 0x00000018 op address R31 0x0000001C 32 General Purpose Registers 32 PC = 0x0000001C 0xfffffffc 0xfffffffc

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3 Architecture vs. organization (3)

Pentium 4

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Architecture vs. organization (4)

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4 Architecture vs. organization (3)

¡ Often: computer architecture = Instruction Set Architecture (ISA) ¡ The true Hardware-Software interface ¡ The most important abstraction of computer design

ApplicationApplication Programs

Operating System Software

Compiler Instruction Set Architecture Processor I/O System Interface between SW & HW Logic - gates, state machines, etc. Hardware Circuit - transistors, etc. Layout - mask patterns, etc.

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Computer architecture

¡ Why is it useful? ¡ Micro-architecture • Not likely you are going to be architects ¡ Software Designers: • How does software really get executed? • What about software design effects performance ¡ Hardware Designers: • What should go in hardware, what should go in software?

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5 Computer architecture

¡ In practice, we will cover: ¡ Computer architecture • ISA ¡ Computer organization • Processor structure • Processor execution mechanism • Pipelining/Instruction-set parallelism • Memory hierarchy principles • I/O interface ¡ Specialization of architecture/organization • Non-conventional architectures • Multimedia extensions (some)

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Computer architecture

¡ Interaction with many disciplines

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6 Objective

¡ Before getting into the details, we must address: 1. Technology trends 2. Cost issues 3. Performance issues

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Technology trends

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7 A brief computer history

¡ 1940s-50s - Vacuum Tubes ¡ 1950s-60s - Discrete Transistors ¡ 1960s-70s - Discrete ICs (e.g., TTL) ¡ 1970s-present - LSI and VLSI

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A brief computer history (2)

ENIAC - 1940s IBM 360 - 1960s (Vacuum Tubes) (Transistors)

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8 A brief computer history (3)

DEC VAX 11/780 - 1970s (Discrete IC’s) Intel 4004 - 1970s (First Microprocessor)

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A brief computer history (4)

Apple II Computer MOS Technology 6502

1970s

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9 A brief computer history (5)

Intel 8088 (LSI Microprocessor) Original IBM PC

1980s

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A brief computer history (6)

Pentium® III PowerPC 7400 (G4) 28M transistors / 733MHz-1Gz / 13-26W 6.5M transistors / 450MHz / 8-10W L=0.25µm shrunk to L=0.18µm 1990s L=0.15µm

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10 A brief computer history (5)

Pentium® 4 Pentium® 4 “Northwood” 42M transistors / 1.3-1.8GHz / 49-55W 55M transistors / 2-2.5GHz L=0.18µm L=0.13µm ...today

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A brief computer history (6)

...the next step... 22

11 Building blocks

¡ Current dominant technology (for digital circuits!): Complementary MOS (CMOS)

¡ Other technologies: ¡ Bipolar (e.g., TTL) ¡ Bi-CMOS - hybrid Bipolar, CMOS ¡ GaAs - Gallium Arsenide (for high speed) ¡ SiGe - Silicon Germanium (for high speed, RF) Used for different targets

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¡ CMOS transistor (n-type) ¡ Basically, a switch

SiO2 Gate D Insulator L G=1 W Source G Drain n+ n+ channel S G=0 p substrate

¡ Technology characterized by the value of L (transistor length) ...trend... ¡ Feature size 2002: L=130nm ¡ Today L=0.13 µm (!) 2003: L=90nm 2005: L=65nm?

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12 CMOS scaling

¡ Features size scales down quite fast ¡ 2001 forecast

Year 1995 1999 2001 2003 2005 2008 2011 2014 µm 0.35 0.18 0.13 0.10 0.08 0.07 0.05 0.034

¡ And even faster than forecasted ¡ 1997 forecast

Year 1995 1998 2000 2003 2007 2010 2013 µm 0.35 0.25 0.18 0.13 0.10 0.07 0.05

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An example: memory chip

¡ IBM J. R&D, Jan/Mar ‘95 ¡ Evolution from 4 – 256 Mb Cell Layouts ¡ 256 Mb uses cell with area 0.6 µm2

4Mb 4 Mb Cell Structure

16Mb

64Mb

256Mb

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13 Moore’s Law

¡ In 1965, Gordon Moore predicted that transistors would continue to shrink, allowing: ¡ Doubled transistor density every 18-24 months ¡ Doubled performance every 18-24 months

¡ History has proven Moore right

¡ But, is the end in sight? ¡ Physical limitations: quantum effects create fundamental limits as approach atomic scale ¡ Economic limitations

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Orders of magnitude

1 cm 1 mm 0.1 mm 10µm 1 µm 0.1 µm 10 nm 1 nm 1 Å

Chip size Diameter of 1996 devices 2007 devices Silicon (1 cm) Human Hair (0.35 µm) (0.1 µm) atom (25 µm) radius (1.17 Å)

Deep UV X-ray Wavelength Wavelength (248 nm) (0.6 nm)

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14 Microprocessor Trends (1)

100,000,000

Pentium 4: 55 million 10,000,000 Alpha 21264: 15 million Moore’s Law Pentium Pentium Pro: 5.5 million 1,000,000 i80486 PowerPC 620: 6.9 million

i80386 Alpha 21164: 9.3 million i80286 Sparc Ultra: 5.2 million 100,000 Transistors

i8086 10,000 i8080 i4004 Log scale! 1,000 1970 1975 1980 1985 1990 1995 2000 Year Current trend: doubles every 18 month => +54% /year 29

Microprocessor Trends (2)

¡ Intel family

Year Chip L transistors 1971 4004 10µm 2.3K 1974 8080 6µm 6.0K 1976 8088 3µm 29K 1982 80286 1.5µm 134K 1985 80386 1.5µm 275K 1989 80486 0.8µm 1.2M 1993 Pentium® 0.8µm 3.1M 1995 Pentium® Pro 0.6µm 15.5M 1999 Mobile PII 0.25µm 27.4 2000 Pentium® 4 0.18µm 42M 2002 Pentium® 4 (N) 0.13µm 55M

Source: http://www.intel.com/pressroom/kits/quickreffam.htm

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15 Microprocessor Trends (3) Relative speed 1200 DEC Alpha 21264/600

1000

800

600 DEC Alpha 5/500 400 DEC DEC Alpha 5/300 HP IBM MIPS MIPS AXP/ 200 9000/ RS/ 500 DEC Alpha 4/266 Sun M M/ -4/ 750 6000 260 2000 120 IBM POWER 100 0 87 88 89 90 91 92 93 94 95 96 97

Current trend: doubles every 18 month => +54% /year 31

DRAM Memory Trends

1,000,000,000 year size(Mb) cyc time 100,000,000 1980 0.0625 250 ns size 10,000,000 1983 0.25 220 ns 1986 1 190 ns 1000x 1,000,000 1989 40.5x 165 ns 1992 16 145 ns 100,000 1996 64 120 ns 2000 256 100 ns 10000

1000 Log scale! 1970 1975 1980 1985 1990 1995 2000 Year Size trend: ~doubles every 18 month => +54% /year Speed: ~ doubles every 10 years! => +9% /year

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16 Memory-processor gap

¡ It is not just a matter of faster processors!!!! ¡ … but this only a part of the picture

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Summary - Technology Trends

¡ Processor ¡ Logic capacity increases ~ 50% per year ¡ Clock frequency increases ~ 20% per year ¡ Cost per function decreases ~20% per year

¡ Memory ¡ DRAM capacity: increases ~ 60% per year (4x every 3 years) ¡ Speed: increases ~ 10% per year ¡ Cost per bit: decreases ~25% per year

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17 Summary - Technology Trends

¡ SIA Roadmap (2001)

Note: 50nm = 5*10-9 m Silicon atom O(10-10m)

¡ Message: • Scaling improves logic speed & density • Scaling increases power!

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Power constraints

¡ Projecting power consumption ¡ Will soon get to KW? ¡ Yes, if we do not use power reduction ? solutions

¡ It is not just a matter of faster processors! (again)

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18 Wires vs. gates

¡ Scaling applies to transistors as well as to wires ¡ Wire scaling means OLD NEW H H L L W W ¡ Capacitance does not scale well • Ground capacitance scales • “Lateral” capacitance increases • Overall capacitance increase w.r.t. gate capacitances ¡ Higher capacitance C • Longer delays (T=RC) • Higher power consumption (P=CV2)

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Wire vs. gate delay

¡ It is not just a matter of faster logic!

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19 Cost issues

¡ Common belief ¡ Performance is top priority ¡ Power almost top priority ¡ Area (size) is irrelevant • Real estate on a chip is not a problem

¡ However, chip cost is directly related to area…

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VLSI Processing

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20 Integrated Circuits Costs

IC cost = Die cost + Testing cost + Packaging cost Final test yield Die cost = Wafer cost Dies per Wafer * Die yield

π * (Wafer_diam/2)2 π * Wafer_diam die per wafer = - - test dies Die Area (2 * Die Area)1/2

−α Defects_per_unit_area * Die_Area Die Yield = Wafer yield * { 1 + } α Die Cost roughly ∝ die_area4 41

Examples

Chip Metal Line Wafer Defect Area Dies/ Yield Die Cost layers width cost /cm2 mm2 wafer 386DX 2 0.90 $900 1.0 43 360 71% $4 486DX2 3 0.80 $1200 1.0 81 181 54% $12 PowerPC 601 4 0.80 $1700 1.3 121 115 28% $53 HP PA 7100 3 0.80 $1300 1.0 196 66 27% $73 DEC Alpha 3 0.70 $1500 1.2 234 53 19% $149 SuperSPARC 3 0.70 $1700 1.6 256 48 13% $272 Pentium 3 0.80 $1500 1.5 296 40 9% $417

¡ From "Estimating IC Manufacturing Costs,” Linley Gwennap, Microprocessor Report, August 2, 1993, p. 15

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21 Logic vs. I/O

¡ Scaling affects speed of logic ¡ Only marginally affects speed of devices! ¡ Impact of scaling on computation:

application Web surfing

¡It is not just a matter of faster processors! (again)

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In summary

¡ Overall system performance depends on: ¡ Processor speed ¡ Memory architecture ¡ I/O system ¡ Performance are constrained by: ¡ Power consumption ¡ Area (translates into cost) ¡ Do not neglect “hidden” costs ¡ Technological issues • Wires (delay and power) cost dominates gate cost • Small feature sizes imply increasing “parasitic” effects ¡ Impact of software

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