Cost and Performance

Goal Understand involved in the design of computer systems Previous lecture Goal Understand Engineering methodology Design techniques Correctness criteria Evaluation methods Technology trends involved in the design of computer systems

Cost Components

Chip Cost Chip cost is primarily a function of die area increases much faster than linearly due to yield going larger gives diminishing performance returns

Chip Cost Die Cost goes roughly with die area4 chip cost = Die cost + Testing cost + Packaging cost Final test yield Die cost = Wafer cost Dies per Wafer * Die yield Die Cost goes roughly with die area4

Real World 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”by Linley Gwennap, Microprocessor Report, August 2, 1993, p. 15

What is Relationship of Cost to Price? Component Costs Direct Costs (recurring costs): labor, purchasing, scrap, warranty Gross Margin (nonrecurring costs): R&D, marketing, sales, equipment maintenance, rental, financing cost, pretax profits, taxes Average Discount: volume discounts and/or retailer markup

Price vs. Cost Figures 1.7 and 1.8

Performance Time to run the task Tasks per day, hour, week, sec, ns … Seoul to Pusan 10 hours 1 hour Speed 100 km/h 1000km/h Passengers 5 100 Throughput 500 100,000 Sonata Boeing 727 Time to run the task Execution time, response time, latency Tasks per day, hour, week, sec, ns … Throughput, bandwidth

Performance and Execution Time Execution time and performance are reciprocals Execution Time(Y) Performance(X) ---------------- = --------------- Execution Time(X) Performance(Y)

Performance Terminology “X is n% faster than Y” means: Execution Time(Y) Performance(X) n ----------------- = -------------- = 1 + ----- Execution Time(X) Performance(Y) 100 n = 100(Performance(X) - Performance(Y)) Performance(Y) n = 100(Execution Time(Y) - Execution Time(X)) Execution Time(X) Example: Y takes 15 seconds to complete a task, X takes 10 seconds. What % faster is X?

Benchmark Programs 1. Real programs - SPEC benchmarks 2. Kernels - Livermore Loops and Linpack 3. Toy benchmarks - Quicksort, etc 4. Synthetic benchmarks - Dhrystone and Whetstone

SPEC: System Performance Evaluation Cooperation http://www.spec.org First Round 1989 10 programs yielding a single number Second Round 1992 CINT92 (6 integer programs) and CFP92 (14 floating point programs) Different compiler flags are allowed for different programs Third Round 1995 CINT95 (8 integer programs) and CFP95 (10 floating point programs) Same compiler flags for all programs of a given language measures both execution time and throughput Fourth Round scheduled to be completed by 1999

SPEC Results

SPEC Results

Other SPEC Benchmarks SFS97 - NFS Performance Web96 - WWW Server Performance HPC96 - High-end System Performance APC, MBC, PLB, OPC, XPC - Graphics System Performance

Summarizing Performance Arithmetic mean Represents total execution time Harmonic mean Consistent independent of reference Geometric mean

Amdahl's Law: assessing enhancement Speedup due to enhancement E: ExTime w/o E Performance w/ E Speedup(E) = ------------- = ------------------- ExTime w/ E Performance w/o E Suppose that enhancement E accelerates a fraction Fractionenhanced of the task by a factor Speedupenhanced, and the remainder of the task is unaffected. What are the new execution time and the overall speedup due to the enhancement?

Amdahl’s Law ExTimenew = ExTimeold x (1 - Fractionenhanced) + Fractionenhanced Speedupenhanced 1 ExTimeold ExTimenew Speedupoverall = = (1 - Fractionenhanced) + Fractionenhanced Speedupenhanced

What’s the implication of Amdahl’s law for computer architects? Integer instructions memory FP instructions others After adding a pipelined integer instruction execution unit and cache memory (with FP emulation) Integer instructions memory FP instructions others

Aspects of CPU Performance CPU time = Seconds = Instructions x Cycles x Seconds Program Program Instruction Cycle Inst Count CPI Clock Rate Program X Compiler X (X) Inst. Set. X X Organization X X Technology X