On a hardware level, different machines have different physical RAM capabilities. This is usually governed by the processor and/or chipset architecture’s capacity to address x number of memory-locations. Also, of course, the amount of RAM that can be used is governed by the number of RAM-slots, and the capabilities of the RAM-controllers.

On a software level, theoretically, a 64-bit operating system is capable of addressing thousands of terabytes of memory; but in reality this could overcomplicate things and cause development costs to rise out of proportion: Therefore most 64-bit operating systems are only capable of addressing a few hundred gigabytes maximum. Going back to hardware; even this amount of memory would, at the time of writing, take up a lot of space on the motherboard. Generally most motherboards available today will be able to utilise anything between 8 and up to 32 GBs RAM as a maximum.

So how much RAM do I need? How much should I have installed?

That depends on a number of factors: Firstly; are you running a 32 or a 64-bit operating system? If you’re running a 32-bit operating system then you won’t need any more than 4 GBs, and the machine won’t see all of that either. – Having said that; the more the merrier. – Up to 4GBs with a 32-bit OS, that is, and as much as you like/can install, for use with a 64-bit OS.

I have a computer running 32-bit Windows XP Professional SP3 on an AMD Athlon 64×2 dual-core processor, with 2GBs DDR2 RAM without any problem. I’ve even set the registry to commit all operations to RAM rather than the paging file, and it’s ‘happy as Larry. The most memory-intensive thing I do on it is search through thousands of large files, which sometimes takes it to the wire, but nonetheless, it’s working fine.

I also have a computer running 64-bit Windows 7 Home Premium on an AMD Phenom x3 triple-core processor. It has 8GBs RAM installed; although it rarely uses more than 5, no matter what I do on it. I don’t use many memory-hungry resource-hogging, graphics-intensive programs on it though. If I did I might use all 8MBs and need more. I know of someone who has fitted and used all 16MBs of memory on their Mac; so it varies from person to person.

A 64-bit OS should run on tickover quite easily with only 2GBs RAM, and have some to spare. I recommend a minimum of 4MBs, personally though, for normal use, with a 64-bit OS.

Can I have “too much RAM”?

In short, in the case of a 64-bit OS; no: If you have more RAM installed than the computer can use at the time, it simply won’t use it until and if ever it needs it.

Even in the case of a 32-bit OS, you can install 32 GBs if you like, as long as you don’t mind the fact that the operating system will never see more than 4 of those gigabytes.

A 64-bit operating system will see it though; whether or not it has to use it: So install it, why not, if you can and if you can spare a few extra readies: At least you’ll know it’s there for if the machine ever needs it.

Any questions? Anything to add? Come on, don’t be shy; there’s a comment box somewhere below, and it’s there to be used.