The purpose of this project was to obtain a component wise breakdown of power consumption for a modern laptop. We measured the power usage of the key components in an IBM ThinkPad R40 laptop using an Agilent Oscilloscope and current probes. We obtained the system wide power consumption breakdown for the following components: CPU, optical drive, hard disk, display, graphics card, memory, and wireless card subsystems. Due to the limitations of our measurement equipment, we had to use a combination of direct measurement approach and subtractive measurement approach. We found that total system power consumption varies a lot (8 W R 30 W) depending on the workload. We also found that though power saving techniques such as DVS can reduce CPU power considerably, the total system power is dominated by CPU power in the case of CPU intensive benchmarks. Display is the other main source of power consumption in a laptop. We found that reducing the backlight brightness can reduce the system power significantly, more than any other display power saving techniques. Finally, we also observed that Windows OS is more power efficient than Linux, as Windows has ACPI support. Last but not the least, we were successful in not destroying the laptop (a fear of all our colleagues), but still get more accurate numbers than simple input supply measurement.
Also available some code used in the project. zip
| The disassembled laptop | |
| Measuring system power | |
| Measuring hard drive power | |
| Measuring LCD power | |
| Incredibly, the thing still works! | |