TuneUp offers our Mac users the choice of a 64 bit or a 32 bit version of our software.  For those users who's systems are 64-bit capable, we highly recommend it, and in fact, we default to this version.  Some users (described in the 32-bit vs 63-bit Versions for Mac help topic) are unable to run the 64-bit version, but the majority of our users can, and starting with TuneUp 2.4.6, those Mac Users with an Intel Core Duo 2 or an Intel Xenon processor and Snow Leopard OS or newer will benefit from our new 64-bit version.  

Why does it matter?

There are noticeable speed boosts associated with running in 64-bit mode. The Intel processors that power Macs have built-in math routines that operate more efficiently in 64-bit mode, processing tasks in fewer steps. That means that certain math-intensive tasks will see a speed boost running within 64-bit applications.  The application will have access to a "full 16 exabyte virtual address space", which is overly-complicated tech-talk for "is faster and uses memory better".

One technical detail that is important to note:  If you’re running a Mac powered by an Intel Core 2 Duo processor or an Intel Xeon processor, your Mac is 64-bit "capable", and that's all you really need to know. Snow Leopard and Lion  run 64-bit-capable applications in 64-bit mode regardless of whether it’s "booting" into a 64-bit or 32-bit kernel.  We bring this up, as there is a lot of confusion out there regarding what 64-bit means for the average user, and we just want to point out that you will gain the advantage of 64-bit capable applications regardless of which "kernel" your machine boots into -- this is a technical and advanced issue, and as far as using TuneUp is concerned, you need not worry about it.