The process runs out of memory, not the machine.
That's not true of 64-bit Autocad. With 64-bit Autocad on a 64-bit OS, the process can address far more memory than you can install on your system.
This should be true in a properly written process, but I watch the resources, and it never gets past 1/3rd of the available resources before dying out with exceptions. I venture the memory address is causing the fault and not the amount of memory to address. Maybe once the floating points go beyond the ceiling for that address and becomes a scientific number instead of an integer?
The code may still be 32 bit for the process used even though it is a 64 bit version of AutoCAD?
I'm making a bunch of stupid mental punts at what the problem may be but it isnt the OS or the hardware out of memory.