What's my bottleneck?

If you have 4 slots it's always best to put matching sticks in pairs.

So if you have two sticks you would want to place them as follows:
[X] [ ] [X] [ ] or

[ ] [X] [ ] [X]

some motherboards will color code the paired slots.

I don't have much experience with mismatched sets of RAM but it might be more beneficial to remove one of the sticks and leave the 4GB unpaired.

Buy 2 4gb sticks or 4 2gb sticks with the highest frequency u can. Always check ur motherboard for specs before upgrading ram. Check for a gb max and make sure the speed will be ok. You shouldnt need to worry about timing if u see that spec.

Interesting. I'll play around with it. That's good to know.

Just to add.
either get matching sticks or RAM- 2x4g sticks, or one single stick 1x4g and put in there.
I personally would not put a 4g with 3x1g.
While i think the new RAM would default to the slowest sticks settings, that may cause problems in itself.

This is the interesting about this problem. And it SCREAMS drivers/firmware of the hardware, or other applications in memory. Computers are deterministic so you can't just say "bad engine" unless you're suggesting they built randomness of performance into the engine.

And not just true randomness... one set of hardware is ALWAYS good and one set is ALWAYS bad. So the random performance degredation method must be tied to hardware IDs of the machine.

That's your machine.. not the game. I have basically the same system with half the RAM as you and I get flawless fps at the highest graphics settings.

I'd have to agree. 2gb of ram is a bottleneck but 3 is usually fine. I'm running 2 sticks of 2gb DDR3 ram in dual channel and my ram definitely isn't a bottleneck cause the game runs smoothly.

I'd say your bottleneck is your processor (if there is a bottleneck...), which you didn't specify in your main post. If it's an old quad core it's likely the culprit, cause more cores doesn't necessarily equal better performance

For instance my Core i3 540 with 2 cores will run the game better than a Phenom 4 core AM2+ from 2008/9 because it has better technology.

You might also have a different driver or software related issue because even with an outdated 4 core you still should be getting pretty good performance regardless...

Never buy ram from best buy ill pm u when I get home from work in about 45 mins

Memory is so cheap today they practicly pay you to take it off their hands.

Get a set of 2x 4GB modules, or even 4X 4GB like I did, since it's so cheap.

$120-140 for 16GB Corsair Dominator DHX 1600Mhz XMP, with fan bracket for mem. I haven't installed it and my mem is doing just fine, even when I overclocked 4 DIMMS from 1600 to 1700.

Then there is something seriously wrong with your system. Coz my game runs like a motherf... on a worse comp, never under 100 FPS.

Many games have problems with the I7 though coz of hyper threading. Each core is simulated as 2 cores, thus reduced speed. And even in a threaded environmenr, many times all the other cores actually have to wait for a calculation to be complete in a single core before they can thread the rest.
So I5 is in most cases a faster CPU for gaming than a I7. While the I7 would performe better in a Windows srv 2008 system handling background tasks.