Administrative Issues

Transcription

1 dministrative Issues Text book ($56.69 in mazon.com) Scanned problem set list Homework 1 announced, due 01/13/10 Quiz, 01/15/10 Graduate students meeting Relevant chapters in textbook? Technology Trends Electronics technology continues to evolve Increased capacity and performance Reduced cost DRM capacity Year Technology Relative performance/cost 1951 Vacuum tube Transistor Integrated circuit (IC) Very large scale IC (VLSI) 2,400, Ultra large scale IC 6,200,000,000 and Technology 2 and Technology 1

2 Defining Performance Which airplane has the best performance? 1.4 Performance oeing 777 oeing 777 oeing 747 C/Sud Douglas DC-8-50 oeing 747 C/Sud Douglas DC Passenger Capacity Cruising Range (miles) oeing 777 oeing 777 oeing 747 C/Sud Douglas DC-8-50 oeing 747 C/Sud Douglas DC Cruising Speed (mph) Passengers x mph and Technology 3 Response Time and Throughput Response time How long it tk takes to do a task Throughput Total work done per unit time e.g., tasks/transactions/ per hour How are response time and throughput affected by Replacing the processor with a faster version? dding more processors? We ll focus on response time for now and Technology 4 and Technology 2

3 Relative Performance Define Performance 1/Execution Time X is n time faster than Y Performance Performance X Y Execution time Y Execution time X n Example: time taken to run a program 10s on, 15s on Execution Time / Execution Time 15s / 10s 1.5 So is 1.5 times faster than and Technology 5 Measuring Execution Time Elapsed time Total response time, including all aspects Processing, I/O, OS overhead, idle time Determines system performance CPU time Time spent processing a given job Discounts I/O time, other jobs shares Comprises user CPU time and system CPU time Different programs are affected differently by CPU and system performance and Technology 6 and Technology 3

4 CPU Clocking Operation of digital hardware governed by a constant rate clock Clock (cycles) Data transfer and computation Update state Clock period Clock period: duration of a clock cycle e.g., 250ps 0.25ns s Clock frequency (rate): cycles per second e.g., 4.0GHz 4000MHz Hz and Technology 7 CPU Clock Cycles Clock Cycle Time CPU Clock Cycles Clock Rate Performance improved by Reducing number of clock cycles Increasing clock rate Hardware designer must often trade off clock rate against cycle count and Technology 8 oeing 777 oeing 747 C/Sud Douglas DC-8-50 oeing 777 oeing 747 C/Sud Douglas DC Cruising Speed (mph) Passenger Capacity and Technology 4

5 Example Computer : 2GHz clock, 10s CPU time Designing Computer im for 6s CPU time Can do faster clock, but causes 1.2 clock cycles How fast must Computer clock be? Clock Rate Clock Cycles 1.2 Clock Cycles 6s Clock Cycles Clock Rate 10s 2GHz Clock Rate s s 9 4GHz and Technology 9 Instruction Count and CPI Clock Cycles Instruction Count Cycles per Instruction Instruction Count CPI Clock Cycle Time Instruction Count CPI Clock Rate Instruction Count for a program Determined by algorithm, IS and compiler verage cycles per instructioni Determined by CPU hardware If different instructions have different CPI verage CPI affected by instruction mix and Technology 10 and Technology 5

6 Tried and True Technique: Peer Instruction Increase real time learning in lecture, test understanding of concepts vs. details s complete a segment ask multiple choice question 1 2 minutes to decide yourself 3 4 minutes in pairs/triples to reach consensus. Teach eachother! 2 3 minute discussion of answers, questions, clarifications $37 PRS Transmitter (not for this course) Peer Instruction: CPI Example Computer : Cycle Time 250ps, CPI 2.0 Computer : Cycle Time 500ps, CPI 1.2 Same IS Which is faster, and by how much? Instruction Count CPI Cycle Time I ps I 500ps is faster Instruction Count CPI Cycle Time I ps I 600ps I 600ps 1.2 I 500ps and Technology 12 by this much and Technology 6

7 CPI in More Detail If different instruction classes take different numbers of cycles Clock Cycles n i 1 Weighted average CPI (CPIi Instruction Counti) Clock Cycles CPI Instruction Count n i 1 Instruction Counti CPIi Instruction Count Relative frequency and Technology 13 CPI Example lternative compiled code sequences using instructions in classes,, C Class C CPI for class IC in sequence IC in sequence Sequence 1: IC 5 Sequence 2: IC 6 Clock Cycles vg. CPI 10/5 2.0 and Technology 14 Clock Cycles vg. CPI 9/6 1.5 and Technology 7

8 Performance Summary The IG Picture Instructions Clock cycles Seconds Program Instruction Clock cycle Performance depends on lgorithm: affects IC, possibly CPI Programming language: affects IC, CPI Compiler: affects IC, CPI Instruction set architecture: affects IC, CPI, T c and Technology 15 Power Trends 1.5 The Power Wall In CMOS IC technology Power Capacitive load Voltage 2 Frequency 30 5V 1V 1000 and Technology 16 and Technology 8