This was another thread where somebody recommended 8GB of ram in a new build. The following is a bit of a write-up on 32GB that I'm going to go ahead and double-post from my response to a General Gaming thread so that the data is also in the HTPC Gaming section. The short of it, Daver, is that 16GB was the correct choice over 8GB, and provably so.
I'm just going to drop this right here.
In my recent upgrade I threw 32GB at the machine, partially as an experiment. With Chrome and nothing else running, you'll notice that Committed is sitting at 4.3GB. It was a bit higher when the system had pretty freshly booted, but then some stuff got written back out at the system's leisure. You'll also notice that Cached is sitting at 21GB. This is stuff that Windows knows I'll want to use at some point. When I do go to use it, it won't need to be read in from a drive, improving my experience. Then there is 8GB just free at the moment.
Sitting on the desktop with just Chrome open I have seen total Commited reach in to the 11GB range. This is before I've even thought about loading a game.
What does this tell us? Well, 32GB is currently a bit overkill, with 24GB as the current ideal. Long-term though it just made more sense to dump all the ram in now. 16GB would also be a very acceptable amount of ram. Windows would still have 12GB to cache stuff with. Most importantly though, nothing would have to be dumped back to disk when the user wants to run something new. There is still plenty of space for Windows to instantly dump a bit of mispredicted cache and fill it with new data.
Here's where it gets interesting. Running 8GB means wasting IO. First, with only 3.5GB for caching, the new thing you want to run probably isn't already in ram. This means waiting for it to read in, effecting your experience. On a 2GB game you'll be okay loading in without too much dumping back out to the swapfile, but only for a bit. Windows really does want to keep some ram open for new stuff, so even though 4.3+2.0 only equals 6.3GB Windows is still going to dump stuff to your swap. While you are trying to play a game. Ugh. Oh, you'll have to wait for that dumped data to read back in too, when you are done with that game for that session. Double-ugh.
What happens when you have 11GB Committed on an 8GB system? Ah, crap. 4GB of data is already dumped to your swapfile on disk. Now you want to read in a 4GB game? Ha! Alright, now we're waiting for 4GB to write out at the same time 4GB is reading in. This is dog slow.
So, as I've repeatedly said, 8GB is starving a machine to death. 16GB is a reasonable amount and certainly the best value. 24GB is roughly ideal, but ram is cheap, why not dump in all 32GB if you're already populating the board with 4 sticks?
Anybody telling you that 8GB is great and 16GB is overkill or pointless is a person speaking from a place of ignorance. Yes, 8GB works, but by no means is it delivering the experience that even a cheap $40 more worth of ram will give you at 16GB. Not knowing
that you are starving your machine is not the same as not starving your machine.