Integrated memory controller enables two channels of high-speed DDR3 1333 MHz memory. This memory controller's lower latency and higher memory bandwidth delivers amazing performance for data-intensive applications.
Intel® Core™ i5 Processor - Overview
The i5's have two memory "channels". You can set your board up to run in single channel mode (which is what you've done by having that odd third stick of RAM), but because the i5's have so much bandwidth, they benefit from using two channels at the same time.
However, in order to get dual channel to work, you have to place your RAM in the right slots. The dimm slots are colored differently for this very reason, so as to identify which channel is which. LGA 1156 motherboards (and that's what you have if you have an i5) use either 4GB's of RAM for dual channel, or 8GB's; they do not use 6GB's. 6GB's of RAM is typical of an LGA 1366 motherboard which has a triple channel memory controller.
Since you're using 6GB's of RAM, you have an extra stick populating the second channel, only because that second channel is not full (ie, not a fourth stick of RAM making 8GB's) your board defaults to single channel. In short, you're not getting the most out of your memory.
I thought that was odd, especially since this came from Dell. If you mistakenly have an i7 (an lga 1366 and not an lga 1156 i7) then your memory configuration would make perfect sense, but since you have an i5, it's a puzzler how Dell let you configure the machine this way?
You will get better performance if you remove the odd stick of RAM or add the fourth. Yes, generally speaking the more RAM you have the better your machine will perform, but not in your case... either remove the odd stick or get another bringing you to the full 8GB's.
If you're a gamer, then don't waste your money on a fourth stick as you will see no performance gains at all... no game uses more than 2GB's of RAM. If you can actually use all 8GB's of RAM, like with some CAD program, then get it, but if you can't, then don't bother.
As for disabling your page file, that is one huge internet myth that refuses to go away. It really won't bring you any sort of performance gains whatsoever... besides, no matter what you do trying to disable the page file, Windows will
always create for itself a page file... so you can end up actually decreasing performance. Some guys have said that it's better to have the page file on another drive (not another partition on the same drive, but on a separate drive), yet, despite their insistence that performance increases, nobody, nowhere has actually ever demonstrated that with benchmarks that prove the point. If they had, everyone would be doing it who could benefit from it.
Windows does a very good job of managing the page file all on its own; let it. With the size of hard drives today, and the large amounts of RAM in most people's systems (4GB's or more) there is absolutely no need for this.
As for ReadyBoost: there is no performance gain to be had if you have 4GB's of RAM or more. RB is/was for systems that had less than 2GB's.
http://blogs.technet.com/b/askperf/archive/2007/03/29/windows-vista-superfetch-readyboost.aspx
