I have an Asus MB P5B <green> and on it is Intel Core2Duo E4600. I am currently using dual channel with GEIL DDR2 2x1GB (400MHz). Since 2GB is not much for todays programs, I want to add another 4GB to have 6GB in total. The memory I want to add is Kingston DDR2 2x2GB (333MHz). The motherboard supports -667 (333MHz), -800 (400MHz) and up to 8GB.

Will this cause me any problems? Sticks will be running in dual-channel. I am being skeptic about the frequency mix.

3 Answers 3



Firstly, why do you want to go with 667MHz memory when you already know that you have 800MHz installed? It's not like you are trying to match the memory speed, i'm just curious?!#@$

Mixing memory frequencies will not cause any issue esp. with your motherboard. As your last post states the higher speed (800MHz) will be defaulted to the lower speed (667MHz) when you mix diff frequencies but still it may run in Dual channel mode.

Try getting 800MHz if you've not yet purchased the memory.

Click here for compatible Kingston memory!



Just a quick update.

DDR2 (Double Data Rate) RAM has total frequency of 800MHz or more. What I saw was Data Rate, not Double Data Rate. If you mix 667Mhz RAM with 800Mhz RAM, all sticks will perform with the lower rate in this case 667MHz.


As you have noted the quicker sticks will fall back to the lower frequency. And as wit said, why cripple your 800 MHz sticks by keeping the 667 MHz ones in your PC? Go for 800 MHz if you haven't already purchased the new ones. This article Memory Scaling on Haswell is very detailed and you don't need to read all of it, but the main points you should take away are the 6 important bullets for memory performance (on the front page):

  1. Amount of memory

  2. Number of sticks of memory

  3. Placement of those sticks in the motherboard

  4. The MHz of the memory

  5. If XMP/AMP is enabled

  6. The subtimings of the memory

Clearly you are being held back by the first point - amount of memory. You will fix that with your purchase, and as long as you make sure they're placed correctly and running in Dual Channel you will reach point #4, which is the frequency. Higher is better; make your own decision based on how badly you want the extra 133 MHz and if it fits within your budget.

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