32 bit and 64 bit are two popular computing architectures used today. Although 32-bit operating systems are still the norm, 64-bit operating systems are becoming increasingly popular. As of June 2010, 46 percent of Windows 7 users are running a 64-bit edition, while the rest are running the 32-bit edition, according to CNET News. In general, the 64-bit architecture is more efficient, but it isn't necessary the better choice for all computer users.
64-bit processors can represent larger chunks of data at a time than 32-bit processors, allowing more efficient handling of all types of computer calculations. Although 64-bit processing is inherently faster, it also requires more temporary storage--random access memory (RAM)--to accommodate the larger chunks of data and provide better system performance.
32-bit operating systems can only use about 3.5 gigabytes (GB) of RAM, even if you install more; 64-bit operating systems can use much more. For example, the 64-bit versions of Windows 7 Professional and Ultimate support up to 192 GB of RAM. According to Microsoft, you need at least 4 GB of RAM in order to experience an increase in system performance with 64-bit processing. If you have less than 4 GB of RAM, moving to 64-bit could actually decrease system performance.
Generally, 32-bit software is compatible with 64-bit versions of Windows, but 64-bit software is not compatible with 32-bit versions of Windows. Microsoft notes that one exception to this is that many 32-bit anti-virus programs do not work in 64-bit versions of Windows. Apple takes a different approach with Mac OS X: There aren't separate 32-bit and 64-bit versions. Instead, there is only one version, and it supports both 32-bit and 64-bit software.
32-bit hardware drivers will not work on 64-bit versions of Windows, but they can work on Mac OS X. According to Macworld, the latest Mac OS X (also known as Snow Leopard or version 10.6) defaults to using a 32-bit kernel--the operating system architecture--which can still run 64-bit applications with all of the associated benefits. However, if you choose to boot with the 64-bit kernel, you will need 64-bit hardware drivers. Macworld notes that there is little benefit to using the 64-bit kernel unless you have more than 32 GB of RAM.
According to Microsoft, it is not possible to upgrade directly from a 32-bit to 64-bit version of Windows or vice versa. If you want to make the change, you will need to perform a clean install, which means that you will need to back up your files and reinstall all your software. Mac OS X already incorporates 64-bit capability, but if you upgrade to Snow Leopard, you will have access to the new 64-bit built-in applications and support for more RAM.