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What price Freedom?

Graphics drivers (for X11 under whatever Free Software operating system you care to use) are one area where Free Software has plenty of room for improvement. My laptop has an nVidia GeForce 9600M in it, which means that there are two drivers I can use for it: the Free Software nv driver, or the proprietary nvidia one. There are qualitative differences (based on what’s available in Kubuntu 9.04 in this case): the proprietary one has the technical advantage that suspend works, compositing works and that logout is faster (because there’s a screen capture thing happening that is used to grey out the display). But there’s also an interesting quantitative difference: power use. This is one I hadn’t thought about at all — the laptop simply gets very warm under normal usage, to the point that my hands get uncomfortable resting on the keyboard. After switching video drivers, though, I thought the laptop felt a lot cooler in normal use. So, measurements. I used a watt-meter that sits between the wall socket and the power brick of the laptop to measure the following:

  • System idle, display on, nvidia driver: 40W
  • System idle, display blanked, nvidia driver: 33W
  • System idle, display on, nv driver: 42W
  • System idle, display blanked, nv driver: 35W

Non-idle the machine draws just as much: clearly regular end-user activities (writing email, writing letters, writing blog entres, but no compiling) don’t exactly stress the machine or draw extra power. Given the numbers, I don’t understand the perceived difference in temperature or comfort of working on the machine. But it does help me put a price on Freedom: two watts.