AM3 Dual Channel Ram Speed

so i haven't really been able to find an exact answer to this...
I have a good grasp on the subject i think... but i'm confused on one little part..

I'm planning on building with a phenom II X3 720 with 4GB (2 x 2GB) DDR3 1333

in a couple years if i decide to add 4GB (2 x 2GB) DDR3 1333 to this - will it then clock down from 1333 to 800?

or is this just on the AM2+/AM3 boards when using DDR2 ram?

thanks for the help guys - this website is the greatest!
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  1. Best answer
    officially it only supports 1333 with 1 chip per channel
    it unofficially supports 1600 with 1 chip per channel

    with 2 chips per channel it only officially supports 1066.

    1333, 1600 might work but not officially supported.

    -- reference article (i found several)

    copy paste is below

    he new Phenom IIs officially support DDR3 memory at up to 1333MHz, but the multipliers are present for 1600MHz operation, as well, as they are in high-end Core 2 and Core i7 systems. Unlike the Core i7, the Phenom II still has "only" two memory channels onboard, not three. I say "only" because each channel of DDR3-1333 memory can transfer up to 10.7 GB/s. Combined with the 2GHz HyperTransport 3 link on each CPU, the total bandwidth available via Socket AM3 is roughly 37.3 GB/s, considerably more than the peak data rate of 10.7 GB/s available via a Core 2 processor's front-side bus (even if it is less than the staggering 64 GB/s possible with a Core i7-965 Extreme and three channels of DDR3 at 1600MHz.) One caveat: the Phenom II only supports 1333MHz DDR3—at least, officially—with a single DIMM in each memory channel. With four DDR3 DIMMs, 1066MHz is the standard. Such limitations are nothing new, of course. Previous Phenoms have long supported 1066MHz DDR2 memory, but only with a single DIMM per channel.
  2. thank you very much!
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