What is the difference between a 32 and a 64 bit installation on a 64 bit machine? I'm about to install Eclipse on my McBook Pro (2.4GHz Core 2 Duo - so 64 bits if I'm not mistaken). What are the consequences of installing a 64 vs a 32 bit package?
The main difference between 32-bit processors and 64-bit processors is the speed they operate. 64-bit processors can come in dual core, quad core, and six core versions for home computing (with eight core versions coming soon). Multiple cores allow for increase processing power and faster computer operation. Thus, software programs that require many calculations to function operate faster on the multi-core 64-bit processors.

Another big difference between 32-bit processors and 64-bit processors is the maximum amount of memory (RAM) that is supported. 32-bit computers support a maximum of 3-4GB of memory, whereas a 64-bit computer can support memory amounts over 4 GB.


More bits means that data can be processed more accurately and in larger chunks.
More bits means our system can point to or address a larger number of locations in physical memory.




Sources / more info: here and here.