I’ve just tried opening Max6 in 64-bit mode for the first time, using the instructions provided by the FAQ. The FAQ states that to launch Max6 in 64-bit mode, click "get info" and switch from there. When I click get info, I only get a check box with "Open in 32-bit mode" — I assumed unchecking this box would launch it in 64-bit. But when I uncheck the box, the FPS of the video I was running in my patch drops from 24 fps to 9, which seems unusual because I would assume that 64-bit would actually increase the speed of Jitter?
I’m running Max 6.1.3 from a 3.4 GHz iMac, 16 GB ram, Mountain Lion, NVIDIA GeForce GTX 680MX 2048 MB
Expected behavior, and yes that check box enables 64bit when unchecked. Many things had to change for 64bit and QuickTime features (losing many of them). The 64 bit version uses QTKit which actually runs 32bit QT as a separate 32bit process. Moving the RAM between processes (with some unfortunately necessary data conversion) is actually expensive to do. In general, anyone working with video will find the 32bit version to be faster/better.
Other things like audio and opengl do not suffer, however, 64bit applications are often no faster than 32bit (or if so, only by a very small factor). The primary advantage is an increased memory pool, and for Max users, floating point max messages now have 64bit resolution (sometimes useful). It’s not much of a performance thing.