How to run 64 bit ATLauncher on i386 debian?

How to run 64 bit ATLauncher on i386 debian?
Added (1). I keep running out of RAM every minute, and I have 2GB unallocated, and cannot allocate them to minecraft due to me having 32 bit java and ATLauncher. How do I allocate more RAM?
Added (2). I was wondering if I could somehow use multiarch to do this.

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