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I have four RAM slots on my motherboard. I'm currently using two. For some reason, when I plug in a third (and fourth), I can only use the new RAM, and not all of it combined. It's a "dual channel" motherboard, and admittedly, I don't know what that means.

So this is probably a really n00b question, but does anyone know why I can't use every slot at the same time? And if I can't use every slot, why even include extra slots?


Update: Here's all the technical specs I know...

I'm running Windows 8 Pro 64-bit (RTM). I'm using DDR3 RAM, but I'm not sure what clock speed or whatever. I have two 4 GB sticks currently installed, and I'm trying to install two more 4 GB sticks, to bring the total to 16 GB. My motherboard has four RAM slots, and it supports "dual channel" RAM, although I'm not 100% sure what that means. Hopefully that's enough information to go on.

share|improve this question
Need more detail! Please edit your question to include the type and capacity of the RAM chips you're using and the model number of your motherboard. – Isaac Rabinovitch Sep 16 '12 at 0:42
Are you using a 32 or 64 bit operating system? – swatso33 Sep 16 '12 at 2:55
You need to know the clock speeds of the RAM. Install the initial RAM, run a program like CPUID or Speccy to determine the clock speed. Remove, install second RAM set. Use same program(s) again, post results here. – cutrightjm Sep 16 '12 at 4:50
what motherboard? – Keltari Sep 16 '12 at 6:15
ASUS P7P55 LX Motherboard – Rev Sep 16 '12 at 12:18

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