We are pleased to announce that our newest viewer update (184.108.40.2061732 AlexIvy) is the first Linden Lab viewer to be built as a 64-bit application on both Windows and Mac. We'd like to send a shout out to the many third party viewer developers who helped with this important improvement! For Windows users whose systems are not running 64-bit yet, there is a 32-bit build available as well; you don't need to figure out which is best for your system because the viewer will do it for you (see below, especially about upgrading your system).
Building the viewer as a 64-bit application gives it access to much more memory than before, and in most cases improves performance as well. Users who have been running the Release Candidate builds have had significantly fewer crashes.
This viewer also has updates to media handling because we've updated the internal browser technology. This version will display web content better than before, and more improvements in that area are on the way. You may notice that this version runs more processes on your system for some media types; this is expected.
There is one other structural difference that you may notice. The viewer now has one additional executable - the SL_Launcher. This new component manages the viewer update process, and on Windows also ensures that you've got the best build for your system (in the future it may pick up some other responsibilities). For Windows systems, the best build is usually the one that matches your operating system. For example, if you're running a 64-bit Windows, then you’ll get the 64-bit viewer. If not, then you’ll get the 32-bit viewer. However, some older video cards are not supported by Windows 10, so the launcher may switch you to the 32-bit build which is compatible for those cards. You won’t have to do anything to make this work - it's all automatic - if you get an update immediately the first time you run this new viewer, it's probably switching you to the better build for your system.
Important: If you have created shortcuts to run the viewer, you should update them to run the SL_Launcher executable (if you don't, the viewer will complain when you run it, and updates won't work). On Macs, the SL_Launcher and Second Life Viewer processes both show as icons on the Dock when running (hover over them to see which is which); this is known bug, and in a future update we'll fix it so they only show as a single icon - we apologize for the temporary inconvenience, but think you'll agree that the performance improvement (quite noticeable on most Macs) is worth it.
Having a 64-bit viewer will help to make your SL experience more reliable and performant (and we have quite a few projects in the queue for this year to that end). However, if you're running older versions of Windows, and especially if you're not running a 64-bit version, you won't be able to get most of those benefits. In our Release Candidate testing, users on 32-bit Windows are seeing crash rates as much as three times as often as those on 64-bit Windows 10. Almost any Windows system sold in the last several years can run 64-bit Windows 10, even if it didn't come with that OS originally. We strongly suggest that upgrading will be worth your while (this is true even if you run a Third Party Viewer, by the way).
About Linux … at this time, we don't have a Linux build for this updated viewer. We do have a project set up to get that back. We're reorganizing the Linux build so that instead of a tarball, it produces a Debian package you can install with the standard tools, and rather than statically linking all the libraries it will just declare what it needs through the standard package requirements mechanism. We'll post separately on the opensource-dev mailing list with information on where that project lives and how to contribute to it.
A fun bit of trivia: AlexIvy name comes from LXIV, the roman numerals for 64.