32 bit vs. 64 bit OSes

If you are considering whether or not to switch/upgrade to a 64 bit OS, this article may give you some helpful background information.

Changes in a 64 bit processor, relative to a 32 bit processor:

1. The address bus is expanded from 32 bits to 64 bits (this allows the processor to address 16 exabytes of physical memory, instead of being able to address only 4 GB).
2. The CPU's registers are expanded in width from 32 bits to 64 bits.

While switching to a 64 bit OS *MAY* speed things up, don't assume it will automatically do so for everything you are running. Here are some reasons why:

1. It is important to catch that the 64 bit processor's data bus did NOT expand in width. Current 32 bit processor's data buses are already 64 bits in width, and have been for a long time, so data is already being moved to/from RAM 8 bytes at a time. 64 bit processors do not change this.
   
2. Unless you switch to 64 bit apps, your 32 bit apps will have to run in the WoW64 emulation layer, causing your 32 bit app to be "thunked up" to 64 bit.

Comparisons amongst 32 bit and 64 bit OSes have been done. This page shows the results of a benchmarking comparison between the 32 bit and 64 bit versions of XP, Vista and Server 2008. Scan through the results and you'll see that in some cases 64 bit is faster, in other cases 32 bit is faster and in yet other cases there is no meaningful difference. Some other comparisons are available here, here, here and here. In short, when running 'normal' 32 bit productivity applications, or similar, there is little if any benefit in switching to a 64 bit OS.