For any software requiring lots of calculations, people always recommend using a 64bit version, they say its faster than the 32bit version of the same software, WHY?
I was having a problem saving my Leaning Tower of Pisa in an .stl version, my PC was giving me an error saying not enough memory..... will this problem be solved if I use a 64bit version?
Does using a 64bit version increase perfomance?
A 64bit Operating System will send 64 bits of information to be processed every clock pulse compared to 32 bits. The 64bit OS does not have the 4G RAM limit of the 32bit OS that will allow the installation of large amounts of RAM in needed.
Using 64bit software will take advantage of the additional processing speed and increased available memory to improve the computers performance and stability.
A 64 bit software can access a lot more memory than a 32bit software, for example if you work with very huge Cad models that take too much memory to load, you would need a 64 bit version of AutoCAD to be able to load everything and prevent crashing.
If your system memory is limited to max 4G, a 32-bit system will do. For anything more than that, I'd suggest to go for 64-bit system and applications. I went for 64 bit about four years ago when I bought my Sempron. Since then, I replaced it with 4 core Phenom, and just a few days ago, for Intel's I7 2600K. Now I can't remember when was the last time I worked on a 32-bit system.
The above answers are all correct and worthwhile, however going to 64 bit and more RAM than 4 Gb, should be followed by an improved CAD rated graphics card if you are looking for better CAD performance.