Computer Architecture 計算機結構. Chapter 1 Fundamentals of Computer Design. Ping-Liang Lai ( 賴秉樑 ). Outline. 1.1 Introduction 1.2 Classes of Computers 1.3 Defining Computer Architecture 1.4 Trends in Technology 1.5 Trends in Power in Integrated Circuits 1.6 Trends in Cost 1.7 Dependability
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Ping-Liang Lai (賴秉樑)
Sea change in chip design: multiple “cores” (2X processors per chip / ~ 2 years)
From Hennessy and Patterson, Computer Architecture: A Quantitative Approach, 4th edition, October, 2006
Since the capacitance is unchanged, the answer is the ratios of the voltages and frequencies:
thereby reducing power to about 60% of the original.
dies along the edge
AMD K8, source: http://www.amd.com
(A greater portion of the cost that varies between machines)
(sensitive to die size)
(# of dies along the edge)
Today’s technology: 4.0, defect density 0.4 ~ 0.8 per cm2
For the small die, it is
This fraction enhanced
This fraction enhanced
Fractionenhanced = 0.4, Speedupenhanced = 10
We can compare these two alternatives by comparing the speedups:
Improving the performance of the FP operations overall is slightly better because of the higher frequency.
Therefore, the fraction of the failure rate that could be improved is 5 per million hours out of 23 for the whole system, or 0.22.
The reliability improvement would be
Despite an impressive 4150X improvement in reliability of one module, from the system’s perspective, the change has a measurable but small benefit.
ICi: the number of times instruction i is executed in a program.
CPIi: the average number of clocks per instruction for instruction i.
Hint: CPIi should be measured because pipeline effects, cache misses, and any other memory system inefficiencies.
Frequency of FP operations = 25%, Average CPI of FP operations =4.0, Average CPI of other instructions = 1.33, Frequency of FPSQR = 2%, CPI of FPSQR =20.
Assume that the two design alternatives are to decrease the CPI of FPSQR to 2 or to decrease the average CPI of all FP operations to 2.5. Compare these two design alternatives using the processor performance equation.
First, observe that only the CPI changes; the clock rate and instruction count remain identical. We start by finding the original CPI with neither enhancement;
We can compute the CPI for the enhanced FPSQR by subtracting the cycles saved from the original CPI: