Mac OS X Mavericks Teaches A Lesson About Energy Efficiency
Apple recently released Mac OS X Mavericks, which all Mac users should happily know, since the new operating system is a free upgrade even for Mac users with very old operating systems (it’s free for Macs dating back to 2007 and operating systems as far back as Snow Leopard). Aside from being free, Mac OS X Mavericks comes with some delightful energy efficiency improvements.
Image Credit: Apple.
Mavericks enables the CPU (which can use in excess of 25 watts) to switch to an idle state, where it uses very little power (as little as a fraction of a watt) — you can consider this somewhat of a sleep mode for CPUs.
I know what you’re thinking… computers have been switching their CPUs to an idle state for a very long time (many years). You’re absolutely correct. However, they were and still are unable to stay in that low-power idle state for long, and are not efficient due to the fact that running programs are constantly trying to do many little tasks and keep calling on the CPU to get back to work.
According to TreeHugger, Mac OS X Mavericks attempts to organize those little tasks in such a way that the CPU gets them done in a certain period and then the CPU is reserved the ability to go to sleep for a longer time.
Imagine getting a day off work, and then being called with questions, or even having to go in to work anyway — not much of a vacation. This is analogous to the average CPU’s situation. But with Mavericks, the CPU really does get its deserved “day off.”
Here’s Michael Graham Richard’s summary of what Mavericks does, which is a summary of John Siracusa’s extensive and detailed review:
To deal with that, Mavericks plays cowboy with all these programs and processes and wrangles them into more tightly packed-together herds so that the CPU can do a batch of them and then power down for a longer period of time. It’s not a perfect metaphor (if you want the details, check out Siracusa’s review), but the general idea is that by keeping requests to the CPU more tightly grouped together, Mavericks allows it to spend more time in low power mode, saving energy.
The OS also does this for the GPU (graphics processing unit/graphics adapter).
That’s not all, however. The new operating system also allocates system resources (RAM, CPU capacity, and other things) more stringently so that programs which aren’t doing anything useful are not able to hog much. This is called App Nap, and it is focused on apps which are hidden behind other windows. In other words, it concentrates your system resources on what you are currently doing by pulling away from apps you really aren’t using.
Similar to App Nap, the Safari browser pauses things in the browser which are out of the margin/not in use, so that you have more power at your fingertips to quickly do what you are focused on, reducing the need to buy a more powerful computer which would consume more electricity.
Regarding RAM, Mavericks also does a much better job of compressing (smooshing) it together in order to free up more memory on your computer.
Your computer puts the programs that are running into its memory (RAM). Nowadays, most computers typically have a few gigs of it (compared to hundreds of gigs of hard drive or SSD space). As long as you have enough RAM to fit all the programs you want, things are fine. But as soon as you run out of RAM, the computer needs to start writing things to the hard-drive and things slow down to a crawl because spinning hard drives are hundreds of thousands of time slower than RAM, and even fast SSDs are thousands of times slower. Mavericks has a new ace up its sleeve to get more out of your RAM: Apple calls it “Compressed Memory”, and it works by transparently compressing portions of what’s in RAM but isn’t currently used using very fast algorithms that work a bit like when you turn a file into a .Zip or a .Rar, or a .JPG vs. a .BMP.
Bottom line is: Compressing things in memory tends to free up about 50% of the space. How much you gain depends on what you’re doing, but in theory, you could fit about 6 gigs of stuff into 4 gigs of RAM.
Overall, these energy efficiency and memory boosts are a big plus, and there are several new features as well, so it looks like Apple did well on this one!
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