Still surfing the web from an old-school Mac? You may want to upgrade shortly. Google has revealed that it's launching the finished 64-bit version of Chrome 39 for OS X this November, and there won't be a 32-bit fallback (like there is with Windows) from that point onward. As the search giant explained when it unveiled the Chrome 38 beta, the bulk of Mac users have 64-bit systems -- it should be safe to move to the newer code without leaving too many people behind. That's cold comfort if you're hanging on to a first-generation MacBook Pro, but the upgrade should finally give most Mac fans a version of Chrome that's as fast and secure as their computer will allow.