Question about RAM on a lap top

So I have a customized DELL XPS L501X with the following specs:

MOBO: DELL 00CKNG
CPU: Intel(R) Core(TM) i5 CPU M 480 @ 2.67GHz @ 1156LGA
RAM: GSKILL 8GB (2x4GB)
HDD: 500GB SATA @ 7200 RPM
VIDEO: NVIDIA GeForce GT 420M


The ram is new. I used to have 4GB NANYA RAM. Now it says that I have 8GB but 7.75 is useable. I am understanding that laptops share the .25 RAM with the GPU. Here is the question:

Based on : microsoft

1. I don't think my GPU is dedicated. How would I check?
2. If my GT420 is onboard, then would disabling this sharing, show a decreased performance in speed while multitasking.

Is there a benchmarking tool that can allow me to look at the comparison of sharing the RAM leaving me with 7.75 GB (with possibly improved GPU performance) or not (showing me with better RAM performance?

EDIT: I think it has descrete graphics card.

EDIT 2: Squirrel meat, don't make any comments about the RAM lol. Get your machine working first lol

CPU-Z/GPU-Z should be able to tell you a lot of base information to start with.

As for where the RAM is going, it's more than likely going to the on-die GPU of your Core i5-480M

The on-die GPU will still get RAM dedicated to it, even if you are running exclusively in dedicated GPU mode. (the theory is that you will want to switch between powerful graphics, and power-saving graphics at some point).

Look in your driver settings for the nVidia Optimus settings to see what you are currently doing as far as switching back and forth between on-die GPU and dedicated GPU.

More than likely your GT 420M has dedicated RAM, either G/DDR3 or GDDR5. (I would almost guarantee it, but I don't know everything, so I won't. :p)

It's highly unlikely that you'd notice the difference between 7.75 and 8 GB of RAM. If your harddrive isn't thrashing from swap and your memory isn't constantly pegged, it isn't worth trying (and even if you are swapping, it's doubtful a quarter GB is going to make the difference).