I did not self-build my computer, I ordered it from an OEM. It was already optimized to run with it's current RAM complement.
And believe it or not, it does make a difference to have more RAM if you're on 64-bit Windows like me. Impulse extracting a download of Supreme Commander takes up about 89% of 9GB. If I had 6GB, it would take up 100%, and everything else on my PC would slow to a crawl.
I once built up a computer from 2GB of RAM all the way to 8GB, over two years. Every upgrade did noticeably improve the speed.
Well, no thats not how windows works.
Windows almost never uses 100% of your ram. If it does it is just for a moment and because it was out of its control.
Windows caps the ram useage so that it never runs out of memory. Going to 6gb, you would still only use about 89% of your memory doing the same thing.Then all windows systems use virtual memory to fill up the gap.
The more ram windows vista/7 has, the more it will use to make its self prepare for anything that it thinks you might use.
Example:
I have a total of 4gb of memory. The lowest amount i use is about 1gb (win 7 64)On occasion i can get it lower or higher.
You with having 9gb of ram, im sure that you use 2-2.5gb at idle.
There are rare programs, installs etc that will utilize a large amount of ram to work. Adobe producs will use up to 16gb of ram if you have it. Most unzipping of files use the hdd a little ram and a little cpu.
Look at your actual ram useage while gaming. It is low, you are never ever using your 89% you might use a total of 4gb, but that is because you are using so much at idle, because you have a greater amount of ram. But your video game is only going to be using XX amount, what ever cap limit it is designed for. Soase is set at 2gb.
You notice improvements from upgrading because...
1. your old system was starving for memory and using your hdd as ram (virtual memory).
2. When you upgraded you got new components and a larger bandwidth of data transfer, mobo, cpu, ram etc. All of these being faster then your old system, thus it was faster.
Windows xp and the games of the erra needed 2gb-2.5gb (i assume most people had 1gb and upgraded to 2gb. There is a noticable difference).
Windows vista/7 needed 3gb-3.5gb.(most people had 2gb and are upgrading to 4gb now they have enough free meory to run programs. There is a noticable difference).
This is where a keyboard with an lcd comes in handy. You can watch your actual cpu/ram useage, to see how much is being used with any given program.
We are not here trying to rag on you. You asked for help and we are trying to give you help. We are al constantly learning, thats what make these forums so great!
We are saying that too may moduales of ram may be slowing down your system. Try runnining your 3 twogb sticks and see if that fixes the problem that you asked for help about.
EDIT:
And you cant optimize a pc/mobo to run with a crtain amount of ram. Your mobo onboard memory controler is capable of using up to 16gb of memory at a time. But the builder of your pc didnt get in there and optimize anything. You wanted more ram, so he said okay.
Back when ddr2 was the rage and ddr3 was just coming out. Bit-tech.net did an article on "how much ram do i need?" This article showesd how when people starting using 4x2gb modules of 8gp of ram, there was a performance hit. It wasnt great, but it was there. I dont have a link atm, but it is a good read if someone finds the link.
Sorry for the long post.