High Performance Computer Architecture: Introduction:

What is Computer Architecture:

Where does Architecture stand?

Levels of Transformation:

Power of Abstraction:

An example: Multi Core Systems

No of transistors on ICs double every year:

Crossing the Abstraction Layers:

Why do we need Computer Architecture:

Simple Computer Architecture Quiz:

Technology Trends

Good Old Moore’s Law (Technology vs Architects):

Speed Doubling Quiz:

Quiz Solution:

Impact of Moore on Speed : Memory Wall:

Processor Performance Metrics:

Speed vs Power vs Weight vs Cost

Power Consumption in a Processor:

Active Power: Capacitance(C) : direct function of chip area. More Area = more C. Technology improvements leads to lesser area, incorporate multiple processors to make it more powerful with same power dissipation. Smaller Transistors are faster, increase in frequency, leading to greater power dissipation. Smaller Transistors lower the supply voltage maintaining the same speed. Too small a voltage also doesn’t lead to optimum frequencies. Can’t increase frequency too much, leads to higher voltage levels. Doubling the Supply Voltage will Quadruple the Power Supply.

Active Power Analysis:

Static Power : Analogy with Water Valve It prevents lowering the voltage too much. Consider circuits like tap, although the valve is closed, The pressure(V) is controlling the valve. In a transistor the valve is controlled by water pressure from another valve (V) If the valve is closed and the pressure applied is not enough(V), water will leak (I) Therefore leakage current increases when Voltage(Water Pressure is reduced)

The Optimum Power consumed should be somewhere in between the graph:

Wafer Cost Reduction: The number of good chips being manufactured/fabricated is a key factor for an organization’s revenue. Smaller sized working chips give a higher yield % as they occupy lesser area. Wafer might have defects due to impure Silicon or impurity caused by the fabrication steps.

Fabrication Yield Example:

More Bang for your Buck:

Metrics and Evaluation:

Parameters for Metrics and Evaluation: What does better mean in Computer Architecture? Is the speed (GHz) or the Memory size(GB)? Latency and Throughput are two key performance parameters. Latency: time taken from start to end for a process Throughput: Number of computations per second (#/second)

Performance:

Comparing CPU/Processor Performance:

Speed Up:

Measuring Performance:

Measuring Performance(Inaccurate Way):

Benchmarks (Accurate Way of Measuring Performance):

Summarizing Performance(Average Execution Time Preferred over Average Speedup):

Summarizing Performance II (Averaging Speedups not preferred): Speed up of average Execution time not the same as average of speed ups of the individual applications. Geometric Mean can be used to average speed ups

Iron Law of Performance in CPU:

Iron’s Law for Performance – II :

Diminishing Returns on 1-Dimensional Improvement: