This question has been popping up in my inbox with increasing regularity over the past few weeks and composing individual responses is eating into my gaming time (damn those Steam sales!). So I can free up some more time for Skyrim and Deus Ex: Human Revolution (yeah, I know, I'm late getting to that game), here's my definitive answer to the question 'How much RAM do I need?'
Note: These figures apply to Windows, Mac and in most cases Linux.
1GB
Consider 1GB the base minimum. 1GB of RAM is enough for basic operations like web browsing (don't expect to run a browser with dozens of tabs open though) and email, and some word processing and light image editing.
Gaming with this much RAM is going to be painful, and ripping media will pretty much take over the entire system, and forget about any video editing.
I'm not making a strong case for 1GB of RAM simply because I don't like being limited to 1GB of RAM.
2GB
I now consider 2GB to be the minimum for a modern operating system (read that carefully). You might get away with less, but chances are that it's going to make you shout a lot fo bad words at your system.
With 2GB you should be able to do pretty much everything with your PC that a PC can do - gaming, image and video editing, running suites like Microsoft Office, and having a dozen or so browser tabs open all become possible. 2GB is also enough to run a hardcore suite of apps like the Adobe Master Collection CS5.5 (so says Adobe ... but if you've got $2,500 to put down for the software, you should be able to afford more RAM!).
Bottom line - If you've got a system with 2GB of RAM and it feels slow, add more RAM!
4GB
We're now getting into serious territory. If you're running a 32-bit operating system then with 4GB of RAM installed you'll only be able to access around 3.2GB (this is because of memory addressing limitations). However, with a 64-bit operating system then you'll have full access to the whole 4GB.
The difference in performance between a system with 2GB of RAM and one with 4GB is like night and day. Even on a 32-bit system that limits the RAM to a little over 3GB, the performance boost is well worth the cost. Not only do application run faster, you can run more applications simultaneously (handy if you run suites like Microsoft Office or Adobe Master Collection).
I recommend 4GB of RAM for all but the most basic of systems.
8GB
Note: You will need a 64-bit operating system to make use of this much RAM.
Now we're into hardcore/performance territory. If you're building a gaming PC, I recommend 8GB of RAM. If you're building a machine dedicated to photo of video editing, I recommend 8GB of RAM. If you want a fast PC, I recommend 8GB of RAM.
8GB of RAM is not expensive either. Sure, get the OEM to fit it into a new system and you're likely paying a premium (especially if that OEM is Apple), but you can buy 8GB of RAM aftermarket for under $50 (faster the RAM, the more expensive it is, but at the time of writing 2GB of branded DDR3 1333 RAM can be found for about $12).
12GB/16GB+
Note: You will need a 64-bit operating system to make use of this much RAM.
Is there a case for more than 8GB of RAM? Sure there is, but the bang for the buck trails off. Gaming systems don't really benefit from more than 8GB of RAM (I've rarely seen Skyrim consume more than 1GB of RAM, even with the 4GB 'large address aware' patch, although my game is largely unmodded).
The time when more than 8GB of RAM becomes useful and starts paying for itself is when you're running a number of resource-heavy applications simultaneously. Try running Premiere Pro, Photoshop and After Effects side-by-side on a system with 8GB of RAM and then bump that up to 16GB and feel the difference!
More than 16GB ... if you need this sort of RAM horsepower in a desktop, you're doing some heavy lifting!
