OS X 10.9 Mavericks: The Ars Technica Review

8 November 2013Apple

John Siracusa wrote 24 pages detailing OS X Mavericks for Ars Technica. Here are a few of the new features that impress me the most:

The price:

After eliminating the trip to the store (or the package delivery), the other major knob Apple can turn to drive adoption of new OS X releases is the price. And turn it has, dropping the price of the Mac operating system steadily over the past five years, hitting $19.99 with Mountain Lion. Mavericks follows the trend to its logical conclusion, finally joining iOS at the magical price point of free.

Close multiple Safari tabs quickly:

Safari takes another page from the Chrome playbook by delaying the resizing of tabs after a tab is closed. Clicking the “x” button on a tab to close it and then clicking repeatedly on that same spot without moving the cursor will close all the tabs to the right of the original tab. The imitation is not perfect, however. Safari resizes the remaining tabs once all the tabs to the right of the original tab are closed. Chrome takes the extra step of resizing the tabs to the left of the original tab, placing their close buttons beneath the cursor as well, when possible—something for Apple to add to Safari 7.1, perhaps.

Compressed memory:

What is RAM for if not to be used? Ah, but as the aforementioned tech-savvy Mac users know all too well, when OS X runs out of RAM, it starts copying data from RAM to swap files on disk. If that same data is needed again soon, it has to be read back from disk. If RAM is still tight, some other data in memory has to be evicted from RAM and written to disk to make room for the incoming data. If this process keeps repeating itself, you have what’s known as “thrashing,” where the system is spending most of its time ferrying data between RAM and disk.

Data spilling over from RAM to disk may not seem like such a big deal if you don’t recall exactly how much longer it takes to get information from disk than from RAM. Reminder: it takes hundreds of thousands of times longer to read data from a spinning hard disk than from RAM. SSDs are much faster than spinning disks, but they’re still hundreds of times slower than RAM.


In Mavericks, the OS has one more option before it has to resort to swapping: compressed memory. Mavericks will find the least-recently-used data in memory and compress it, usually to about half its original size. Et voilà, more free memory.

Like the HFS+ compression feature introduced in Snow Leopard, compressed memory trades relatively abundant CPU cycles for decreased disk I/O. The compression and decompression process is extremely fast, using the WKdm compression algorithm, and it will run in parallel, taking advantage of multiple CPU cores.

Intuitively, a multi-core CPU grinding away compressing data in RAM does not seem like a winning strategy to save energy. But our intuition is often wrong when it comes to real-world energy use on modern hardware. Remember, it’s a race to sleep! Avoiding shuttling data between RAM and that hundreds-of-times-slower-than-RAM SSD is a big win as long as the compression task can be completed in a fraction of the time it would take to access the SSD. It can be, and it is.

Despite being a free upgrade, I am happier with the progress made in Mavericks than I was with either Lion or Mountain Lion, both of which I paid for. The move away from skeuomorphic design is appreciated, although it isn’t gone completely. The Mail app has been improved – after a few initial bumps – to work better with Gmail. And as I mentioned last week, you now get a choice of snooze lengths for Notification Center alerts. Overall, it’s a nice set of incremental improvements at a great price.