Q: Does the 64-bit version of an OS use more memory than the 32-bit version of the same OS?

A: You now have the choice to use the 32-bit or 64-bit version of most Windows OSs today (except for the latest server OS, Windows Server 2008 R2, which is now exclusively 64-bit). The reasons to go 64-bit include greater access to memory for 64-bit applications, access to more than 4GB of physical RAM (although often systems only see around 3GB because other devices use up the memory address space), and improved security capabilities. However, a common question is, does the 64-bit version actually use more memory than the 32-bit counterpart?

The answer is yes, but it’s generally only a small difference, maybe 100MB of extra memory space. That’s not a huge price to pay for the advantages of the 64-bit platform, providing you actually are taking advantage of the 64-bit benefits.

The logical next question is WHY does the 64-bit version use up more memory?

It uses up more memory for several reasons. First, you can run 32-bit applications on a 64-bit OS, which means a 64-bit OS has to load some 32-bit libraries into memory in addition to its native 64-bit libraries, which is the bulk of the memory difference.

Additionally we use 64-bit memory addresses instead of 32-bit memory addresses. This means each pointer to memory takes up 8 bytes instead of 4 bytes, causing some additional memory use there as well. However, that’s unlikely to be a huge factor.

To see more FAQs, please go to John Savill's FAQs page on Windows IT Pro.