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Lecture 3 - Quantitative Analysis (2010-01-19)

# Lecture 3 - Quantitative Analysis (2010-01-19) - 1 Chapter...

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Unformatted text preview: 1 Chapter 1: Quantitative Analysis Chapter 1: Quantitative Analysis Modern Processor Design: Fundamentals of Superscalar Modern Processor Design: Fundamentals of Superscalar Processors Processors Mark Heinrich School of Computer Science University of Central Florida Define and quantify power ( 1 / 2) Define and quantify power ( 1 / 2) • For CMOS chips, traditional dominant energy consumption has been in switching transistors, called dynamic power 2 witched FrequencyS Voltage Load Capacitive Power dynamic × × × = 2 2 / 1 • For mobile devices, energy better metric Voltage Load Capacitive Energy dynamic 2 × = • For a fixed task, slowing clock rate (frequency switched) reduces power, but not energy • Capacitive load is a function of number of transistors 3 connected to output and technology, which determines capacitance of wires and transistors • Dropping voltage helps both, so went from 5V to 1V • To save energy & dynamic power, most CPUs now turn off clock of inactive modules (e.g. Fl. Pt. Unit) 2 Example of quantifying power Example of quantifying power • Suppose 15% reduction in voltage results in a 15% reduction in frequency. What is impact on dynamic power? dynamic dynamic dynamic OldPower OldPower witched FrequencyS Voltage Load Capacitive witched FrequencyS Voltage Load Capacitive Power × × × × × × × × × ≈ = × = = 6 . ) 85 (. ) 85 (. 85 . 2 / 1 2 / 1 3 2 2 4 Define and quantify power (2 / 2) Define and quantify power (2 / 2) • Because leakage current flows even when a transistor is off, now static power important too Voltag Curren Powe • Leakage current increases in processors with smaller transistor sizes • Increasing the number of transistors increases power even if they are turned off • In 2006 goal for leakage is 25% of total power Voltage Current Power static static × = 5 • In 2006, goal for leakage is 25% of total power consumption; high performance designs at 40% • Very low power systems even gate voltage to inactive modules to control loss due to leakage 3 Define and quantify dependability (1/3) Define and quantify dependability (1/3) • How decide when a system is operating properly? • Infrastructure providers now offer Service Level Agreements (SLA) to guarantee that their networking or power service would be dependable • Systems alternate between 2 states of service with respect to an SLA: 1. Service accomplishment , where the service is delivered as specified in SLA 2. Service interruption , where the delivered service is 6 different from the SLA • Failure = transition from state 1 to state 2 • Restoration = transition from state 2 to state 1 Define and quantify dependability (2/3) Define and quantify dependability (2/3) • Module reliability = measure of continuous service accomplishment (or time to failure)....
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Lecture 3 - Quantitative Analysis (2010-01-19) - 1 Chapter...

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