Solved Computer won't use all installed RAM

Hey guys, so I tried to install more RAM, but after I put the sticks in, System information told me only 4GB of the 12 total GB were usable. My setup was two 2GB sticks in ports 1 and 2 and four 4GB sticks 3 and 4. I then switched it around and put the two 4GB sticks in ports 1 and 2, and the two 2GB sticks in 3 and 4. After this 8GB of the 12 were usable. Finally I tried putting the 4GB sticks in ports 1 and 3 and the 2GB sticks in ports 2 and 4 and vice versa.

Any tips?


RAM Sticks

4GB - Newegg.ca - CORSAIR XMS3 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model CMX4GX3M2A1600C9

8GB - Newegg.ca - Kingston HyperX Blu 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model KHX1600C9D3B1K2/8GX


MOBO - Newegg.ca - ASUS P7P55D Deluxe LGA 1156 Intel P55 ATX Intel Motherboard

Hello Nick,

It's best to use RAM sticks that are all identical to avoid having any potential compatibility issues.

You would need to have the 4GB sticks in slots A1 and B1, and the 2GB sticks in slots A2 and B2.

P7P55D - Motherboards - ASUS



Hope this helps,
Shawn

Ok, I always find these issues interesting so here's what I've found out so far:

On the surface, it looks like everything should work; however, I did find one restriction on your motherboard if you are trying to run all 4 sticks at 1600:



The solution may be to set the RAM to run at 1333Mhz which is most likely the native speed associated with your (unknown) CPU.

Also, there could be a conflict between the way the addressable arrays are setup but I saw no restriction regarding that in your mobo manual. I found that the 8GB (2 x 4GB pair) kingston uses a double sided 256x8 scheme for each module but I couldn't determine the configuration for the Corsair. In any event, I am not sure that would be the issue anyway.

I also noticed that all testing of memory on the QVL list always used modules of the same memory size and same memory manufacturer. You could also try running with 3 modules to see if that makes any difference. Yes, I know that will kill the dual channel but this would just be for testing and maybe that might be the best you can do here (if it worked).

Oh, and I'll end my analysis with the standard reminder that anytime one mixes sizes and manufacturers when running a dual channel arrangement can possibly lead to unresolvable problems. Anyway. Good luck.

Brink said:

Hello Nick,

It's best to use RAM sticks that are all identical to avoid having any potential compatibility issues.

You would need to have the 4GB sticks in slots A1 and B1, and the 2GB sticks in slots A2 and B2.


This solved it! Thanks! All 12 GB is being recognized
!
P7P55D - Motherboards - ASUS

View attachment 28859

Hope this helps,
Shawn

Click to expand...

This solved it! Thanks! All 12 GB is being recognized!

You're most welcome. Glad we could help.

Brink said:

Hello Nick,

It's best to use RAM sticks are all identical to avoid having any potential compatibility issues.

You would need to have the 4GB sticks in slots A1 and B1, and the 2GB sticks in slots A2 and B2.

P7P55D - Motherboards - ASUS

View attachment 28859

Hope this helps,
Shawn

Click to expand...

Well I skimmed right past the obvious "assuming" the OP had placed the memory in the proper slots. Good one Brink and congrats to the OP!