There's a good example of the first point in desktop system design as well. If you're playing a graphics-intensive game with your fancy NVIDIA card and feel like taking a screenshot, hitting "PrntScrn" won't help you. This is because the OS has no access to what actually gets sent to the monitor by the dedicated graphics card; the card doesn't transfer unnecessary information back to memory. This has more to do with performance and memory bandwidth I think than energy usage, but it's an example of limiting data transfer on the system level that introduces counter-intuitive behavior on the software level.
You might enjoy these slides from Bill Dally, head of NVIDIA research. (see discussion of data movement starting on slide 10)
http://www.nvidia.com/content/gtc/documents/sc09_dally.pdf
There's a good example of the first point in desktop system design as well. If you're playing a graphics-intensive game with your fancy NVIDIA card and feel like taking a screenshot, hitting "PrntScrn" won't help you. This is because the OS has no access to what actually gets sent to the monitor by the dedicated graphics card; the card doesn't transfer unnecessary information back to memory. This has more to do with performance and memory bandwidth I think than energy usage, but it's an example of limiting data transfer on the system level that introduces counter-intuitive behavior on the software level.
@rbcarlso cool post