DDR3 1600 only running at 400 MHz

I searched a while for a solution to this, but didn't find much helpful. In fact some of it was pretty confusing.

I recently got two 4 GB sticks of DDR3 1600 (corsair vengeance CMZ8GX3M2A1600C9B) but BIOS is only recognizing it as DDR3 800. CPUZ clocks it at 400 MHz, which from what I understand means an effective speed of 800 MHz since it's dual channel. So why isn't it running at 1600 MHz? I read somewhere that your CPU sometimes limits the speed your memory can run at... is this what's happening?

My CPU is an Athlon II x2 and my motherboard is an ASRock M3A770DE (, if this helps. (yes, I know it's not the best board but I want to squeeze as much out of it before I have to upgrade.)
8 answers Last reply Best Answer
More about ddr3 1600 running
  1. Hi, What are the JEDEC and the XMP values in CPU-Z?
  2. Thanks for the quick reply. Here's the results of CPU-Z:

  3. Hello skip to the "In a nutshell" part. I think it has to do with your you guessed. If not at least your BIOS commands

    Just a guess and I am no expert, just reading about it too.
  4. Best answer
    Try manually setting in BIOS the JEDEC 4 values (Memory Clock to 667 and values from CAS Latency to TRAS - 9,9,9,24)
  5. Alexoiu: thanks for the help, I changed the values you said and it seems to be running at 1333 MHz now. Just to make sure I didn't mess anything up (I've never overclocked RAM before) I'll post the new CPU-Z results:

    Will my system be stable with these settings? I'm kinda paranoid about messing with settings like this...
  6. Best answer selected by DarkLordGiggles.
  7. You can run some memory tests (lke memtest) and see if you get any error. Check also the temperatures under load using HWMonitor or similar.
    For some reason the BIOS underclocked the memory. A BIOS update might or might not solve the issue. As long as the system is stable with these values, I'd say it's OK.
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