So if you were using Arma3 'Set Launch options' properly before, i.e for a 32 bit exe which is limited to 3071 MB, then you need to increase -maxMem=3071 to some reasonable portion of your RAM total.
UNIT: Richard Biely, Programmer, Programming Dept.
TO: Arma 3 Dev-Branch Users
OPSUM: Introducing 64-bit Arma 3 - what, why, and how!
In recent years, a growing number of developers have released their games with 64-bit support. Many of our own community have hoped or suspected that, sooner or later, this simply had to happen to our beloved series as well. To live up to your hopes - we are proud to announce that 64-bit Arma 3 is knocking right at your door, now released on Dev-Branch.
But what exactly are the benefits of having a 64-bit game, what does it mean for you as gamers, and why did you have to wait until now? ...