16gb ram only showing 8gb usable, but 16gb installed windows 10 (whatever win 7 ultimate upgraded to)

so basically I bought a second set of corsair vengeance black 4gb sticks, (I had 8gb orginally) upon installing them I found to my surprise windows has recognized there is 16gb installed, however there's only 8gb "usable" I've tried the "advanced boot settings" method and i couldn't get it to use all 16gb, any ideas here? (4x4gb stick layout)
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More about 16gb ram showing 8gb usable 16gb installed windows win ultimate upgraded
  1. What mobo, CPU and model #s of the DRAM? Also what slots are each stick in? Can try raising the DRAM voltage and MC (memory controller) voltage each about + 0.06 or, can provide better numbers w/ the CPU, mobo and DRAM models
  2. mobo : msi gaming 970
    cpu : amd fx 8320
    dram model is : cmz8gx3m2a1600c9 (I think)
    there's only 4 slots, and there's a stick in each slot, like I said I had 8gb before, added the other 8 today, they should be the same ram from what I've looked at. that being said the first pair (orginal pair) are on the far right slots, and the 2nd pair (new) are on far left, and windows is recognizing it as 16gb installed, but only showing 8 is usable, I'm 99% sure these are dual channel, but the other set was too, so theoretically they should be completely usable right?
  3. Try (from CPU) new, old, new, old - go into BIOS and set DRAM voltage to 1.57 and set the CPU/NB voltage to 1.25
  4. So, after booting into bios to confirm the orginal dram was the same model, I figured it out, it wasn't the dram voltage itself, but the dram clock, it was set the default, so I bumped it up to 1600mhz (because that's the advertised frequency for the modules) saved and booted back into windows and it worked! 16gb fully usable, thanks for the help :)
  5. No worries, glad all is well
  6. hi,I have problem ,I got 4x4 ,G.SKILL Ripjaws X Series 4GB 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop ,fireston memory card ,windows 10 home 64 bit is recognizing it as 16gb installed, but only showing 8 is usable, I know it's in the Bios,but I don't know how to fix it.
    i7 CPU 880 @ 3.07 GHz
    graphic card nvidia/Geforce GTX 750 Ti
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