Note: Make reasonable assumptions where necessary and clearly state them. Feel free to discuss problems with classmates, but the only written material that you may consult while writing your solutions are the textbook and lecture slides.
Consider the following table that shows the fraction of power, execution time, and area that can be attributed to each part of a 100mm2 microprocessor chip:
| Processor Component | Power Contribution | Exec time Contribution | Area Contribution |
|---|---|---|---|
| Instruction fetch unit | 30% | 10% | 20% |
| Execution/issue unit | 40% | 60% | 15% |
| Register file | 10% | 5% | 5% |
| Caches | 20% | 25% | 60% |
Your team of designers comes up with the following innovations that impact the performance, power, and area of those individual units by the following amounts (Row 1 of the table below specifies that the innovation to the fetch unit causes the fetch unit's power to increase by 30%, the time spent in the fetch unit to decrease by 50%, and the fetch unit's area to increase by 30%):
| Unit X and Percentage change in unit X | Power | Exec time | Area |
|---|---|---|---|
| Innovation to Instruction fetch unit | +30% | -50% | +30% |
| Innovation to Execution/issue unit | +40% | -60% | +40% |
| Innovation to Register file | +20% | -10% | +120% |
| Innovation to Caches | -40% | +20% | 0% |
Which innovation will you select if you are trying to optimize (note that you could end up selecting none of the innovations too):
This question requires you to generalize Amdahl’s law to the case when multiple enhancements are possible. Three enhancements with the following speedups are proposed for a new architecture:
Speedup1=30, Speedup2= 20, Speedup3 = 15.
Only one enhancement is usable at a time (but multiple can be used over the entire application). If enhancements 1 and 2 are each usable for 25% of the time, what fraction of the time must enhancement 3 be used to achieve an overall speedup of 10 for the entire application ?
You have designed an innovation that improves the CPI of five programs in a benchmark suite in the following way:
| Program A | B | C | D | E | |
|---|---|---|---|---|---|
| CPI of baseline processor | 1.9 | 1.3 | 2.1 | 0.7 | 0.6 |
| CPI with new innovation | 1.7 | 1.2 | 2.2 | 0.5 | 0.7 |
Unfortunately, because of the additional circuits required by your innovation, the clock speed reduces by 5%. What is the bottom-line speedup from your innovation, as reported to:
You run a web-server from your garage to sell ski equipment. Your web server has 20 CPUs, 5 different software packages that handle transactions, and 10 disk drives. The MTTF for each CPU is 500,000 hours, for each software package is 100,000 hours, and for each disk drive is 200,000 hours.