There have been rumors going around about a 64-bit World of Warcraft client possibly going live. Unfortunately, these rumors have also spread a fair share of misconceptions and poor information. I would like to clarify just what benefits a 64-bit client would and would not provide.
First off, if it's not already obvious, you need a 64-bit operating system to use a 64-bit client. 64-bit executable files are not compatible with 32-bit operating systems; however, the opposite is not true. Modern x86-64 Windows operating systems run 32-bit executable files without any real problems. World of Warcraft is currently only offered in a 32-bit flavor, but it is 100% compatible with 64-bit Windows XP, Vista and 7 systems.
One of the main things that people anticipate a 64-bit client would do is improve stability by increasing the usable address space. World of Warcraft - like any other 32-bit application - is normally limited to 2 GB of address space. If a standard x86 application exceeds that limitation, it will crash. There are three ways around this: You can lower the application's memory use, you can rewrite and compile the EXE as 64-bit, or you can use something that is known as a large address aware flag.
Let's look at that third option. A large address aware flag is a flag that's added to a 32-bit application that - at its core - tells the operating system that the program can use more than 2 GB of address space. On a 64-bit operating system, this will double the address space for the application to 4 GB of space. A 32-bit operating system will allow the application up to 3 GB, but only if it's told to explicitly acknowledge the LAA flag. This is not the default behavior, nor is it recommended to do this.
For years, a select few players such as myself hit that 2 GB ceiling and ran into stability issues. Many players may remember hitting this crash in 3.3.5 when there was a large memory leak that needed patching. Fortunately, there were/are tools that can add or remove a large address aware flag from a program, such as one that I shared here:
Come 4.1, this flag is now included by default, as posted here:
What does this mean, though? It means that World of Warcraft running on a 64-bit operating system is able to utilize 4 GB of address space right off the bat, no changes needed. Bringing the rumored 64-bit client into this discussion, you should begin to realize that it wouldn't actually impact stability at all. Players simply should not be exceeding 4 GB of memory usage. Any out of storage crashes they see should be pointing to their cache folder as the culprit. Deleting it should resolve the problem.
Of course, players running a lot of addons with high levels of detail on a 32-bit operating system may still be prone to instability from the 2 GB overhead. Neither a large address aware flag or 64-bit executable would benefit them, though. They will either need to tone down their settings or upgrade to a 64-bit operating system.
Aside from the extra room for address space, a 64-bit client could also theoretically bring some performance gains to the table. What kind of gains would we see? It's really hard to say. A well-written 64-bit application can usually see about a 10% increase to performance at best. Usually the gains are even more negligible, though. Various sites have published benchmark results that put 32-bit to 64-bit head-to-head. Feel free to browse around the Internet for some.
Tying the higher address space to performance, some gains may be noticed if the developers decide to use spare memory for other reasons. For example, a computer with 16 GB of memory may have plenty of RAM to spare. A 64-bit application could use some of that extra memory for caching purposes and the like, shortening load times and possibly increasing framerates.
There are plenty of questions regarding 64-bit vs. 32-bit builds even today. If this thread didn't clarify a specific question you had regarding what 64-bit can and cannot help with, feel free to ask and I will do my best to answer.
The wise speak only of what they know. - J.R.R. Tolkien
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