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Thank you for the link Gordon. I do remain skeptical, however, of the content. I don't know that it's wrong, but its last update is over six years ago, and there seems to be a lack of supporting evidence. It would be easy enough to prove, if true. Somebody could find the current requirements, or could record an xperf trace that shows drivers doing this. Without some sort of recent confirmation I remain skeptical. But, next time I'm looking at an xperf trace I'll watch for signs of this behavior. If I find anything interesting I'll be sure to blog about it.
Sorry for the string of comments, but this sort of post seems to bring out the ad-hominem arguments. A previous commenter said: "Easy: because Microsoft is dumb as a post when it comes to coding." The comment then referenced a Mark Russinovich blog post from 2007 which concluded with "I've learned that the compression engine has been updated in Vista SP1 to perform fewer file operations." So, six years ago Vista had a problem, which was then fixed. I don't think Microsoft is perfect -- my blog is mostly criticisms of their products. But I try to limit my criticisms to products that are current, not an OS that is three versions from the latest.
Gordon Messmer says "I vaguely recall..." someone from another company mentioning something around the time when Vista was introduced... First, citation needed. Second, that's seven years ago so probably not relevant. Third, the claim doesn't seem likely. Maybe Microsoft would check the signatures occasionally, but Microsoft cares about battery life too much to make frequent signature checking seem likely. Extraordinary claims require extraordinary evidence.
Since the poor battery life is on a web browsing test it is quite likely that the difference is not an OS difference but a web browser difference. If we want to be able to say that the OS is at fault then we would need to do a test with the same browser on both platforms -- Chrome perhaps. Although, since Chrome unilaterally raises the platform timer frequency maybe that wouldn't be such a good idea... It would also be interesting to try more tests with comparable machines rather than Apple machines. Otherwise too much home-turf advantage is being ceded to Apple -- see the ACPI tables comment. Microsoft works very hard to try to minimize power draw (I worked with the guys who do this). However they constrained by their desire for perfect backwards compatibility, which significantly limits, for instance, timer coalescing. It's an important topic and I'd love to see more investigations, including deep dives into *why* some scenarios draw more power. That is, I'd love to see power science instead of power speculation. As one example, when doing power-draw benchmarks it is important to monitor the timer frequency with clockres to see if some maladjusted service has raised it.
Comparing Windows and OS X on the same hardware seems like the ideal comparison since it reduces the number of variables, but it actually turns out to be bad science, I believe. Apple supplies the Windows drivers for their hardware and they have no incentive to provide best-of-breed Windows drivers for their hardware. In order to sabotage the Windows results they merely have to not spend a lot of effort on optimizing their Windows drivers. Still, there is clearly something wrong. However I find this line frustrating: > I just wish somebody could explain to me and > Anand why Windows is so awful at managing idle power Wait. Isn't it Anand's job to figure this sort of stuff out? He should use xperf (http://randomascii.wordpress.com/category/xperf/) to find out where CPU time is going, and Intel's Power Gadget (http://software.intel.com/en-us/articles/intel-power-gadget-20) to estimate power draw, and then write an awesome article explaining why Windows is drawing more power. I would love to read that article. If Anand and other tech journalists don't have someone on staff who can do this type of investigation then they need to think about finding someone, IMHO.
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Oct 21, 2013