Installed 6GB ran, but I'm only seeing 4GB...

Hi, I recently built my own computer with 6GB RAM running Windows 7 64 bit, however control panel is saying I have 4GB installed. I also ran msconfig and under advanced options under the Boot tab, the maximum memory won't let me push it passed 4096. Below are the relevant specs for my computer. Thank you in advance!

MOBO - ASUS P7P55 LX
RAM - Obsidian DDR3 1600 (3 @ 2GB)
Graphics Card - Radeon 5770
Processor - Core i5

Ah, so with my current settings I'd have to throw in another 2GB card then I can max out at 8GB?

Open CPU-Z and make sure it shows all 6GB....

Your system is running 6GB ATM, but it looks like it is not in dual channel mode. Not sure if it is the same as AM3 systems but you can run dual channel with either 4 or 8GB on RAM. The P55 support dual channel only meaning a user will normally buy a set of 2x 2Gb or 4x 2Gb DDR3. The 3x 2Gb and 6x 2Gb sets are normally used with the x58 platform. Your best option here is to buy a single stick for a total of 8Gb.

Try this, remove the third module, test your PC with a benchmark like Sandra, Vantage or PCmark. Then install the third module and test again... Compare marks and you should have your answer.