Have we reached a point where game makers are taking advantage of 64bit OSes and allocating more memory to their processes beyond the standard available on a 32bit OS or are games not yet taking advantage of large amount of RAM?
Basically, is it worth spending the money on a 64bit OS and more than 4 gigs for a gaming PC?
(I have rectified my answer. To clarify: every process gets 2 GB of virtual address space. All processes combined can't exceed 4 GB of physical memory)
Actually, yes. There are many misconceptions about the memory limit in 32-bit Windows OSes.
First of all, when I say RAM, this includes every kind of RAM. So not just regular, but also your video RAM. Only physical memory though, not swap/paging.
The maximum available amount of RAM per process for a 32-bit OS is 2 GB. If you have a 64-bit OS, a 32-bit process can allocate up to 4 GB.
Additionally, the entire OS can only address 4 GB for every process combined, while 64-bit OSes can allocate 8 TB.
Also interesting is that this limit adds up to the paged pool. This means that a 32-bit OS cannot use more than 4 GB total, which means 6 GB for all applications including virtual memory. Of course, this has nothing to do with RAM, because the other 2 GB would be stored in the paging file, limited to your hard-drive's speed.
For more information, see Memory Limits for Windows Releases.
A lot of times the bottleneck for your graphics is the video RAM, not the other kind you usually associate when you hear RAM.
Video RAM is located in the video card, and is used to store textures that are used while you're playing, among other things. The higher-resolution textures you want to use, the more video RAM you need. And high-resolution textures are generally the most noticeable thing that makes the graphics look better.
Most games don't do much intensive stuff other than the graphics, because they just don't have time to. So you're probably safe sticking to 4GB of RAM.
Having more RAM won't give you more FPS, if you can run the game at all.
It will make life a bit easier, though.
If you have ample RAM, some or most of the game assets will be already cached while, say, loading it a second time, so it might start, or load levels faster than the first time around.
Currently, 64 Bit OS's don't have any visible advantage than being able to address RAM beyond 4 GB. But that might change with Battlefield 3, for which DICE recommends a 64 Bit OS, though I am not sure if it is for the larger memory use or DX11 support. Either way, I wouldn't invest into anything bound by 32 bit technology anymore.
Well first of all, if you have a 32 bit machine and you have 4 gigs of installed ram in your computer, you are really only utilizing roughly 3.2 gigs.
Second, once you are in the 4-8 gig range, its more about the speed of your memory rather than how much you have. You want something with low latency if possible.
Finally, like Strix said, the huge majority of the time, the bottleneck will either be your video card or your processor, especially if you already have 4 gigs of ram.
I won't matter, much, unless you are doing things other than playing game while playing the game.
IMHO the first thing you should do is to turn off paging. Windows will keep paging on even if you have a large amount of RAM. With ~4GB ram you will almost never run out and by turning off paging significant performance can be gained. There is a detailed discussion here
If you don't see your performance improve then adding ram is helpful
Games themselves don't take advantage of a 64-bit OS yet, but using a 64-bit OS when you have 4GB of RAM will still make a difference when it comes to the amount of memory Windows can actually use.
Even though Intel switched to 36-bit RAM addresses a few years ago, allowing up to 64GB of RAM, Windows enforces a 4GB memory limit on its Home and Professional 32-bit editions. This restriction is higher on its 64-bit editions... but is different in each edition (Home Premium is 16GB).
Furthermore, of this 4GB for 32-bit Windows, any memory-mapped devices will shrink the address pool by stealing memory addresses for its own use. This technique is commonly used by video cards. This means, with a modern 3D accelerator, your RAM pool will shrink down by 512MB-1GB (or more).
There are ways in Windows to access RAM beyond the 4GB limit, but I have yet to see games that use it... and you still lose RAM to the video card. Either way, with more than 3GB of RAM, you ought to use a 64-bit version of Windows.
Generally speaking, if you are running a 64-bit native OS and a 64-bit native game, then yes, it can help. At the very least more RAM means less paging (reading and writing less used sections of memory to disk to free up RAM), and less paging means a faster computer overall. Generally 8GB would be enough so that most games won't compete with the OS for memory and allow for processes to run smoother because again, less paging.
In game specific terms, you can have more/bigger textures in memory as well as more of a level and characters loaded as well, but only if the game is written in such a way as to take advantage of the bigger memory pool. This really only applies to games with dynamic limits.
Its only an advantage if the game is written to take advantage of it: Games who's only limitation is the size of available memory are generally the only ones to see a performance boost by more than 4GB of RAM.
