post #11 of 11
^^^^ Just because RAM has been speed rated to run "up to 2133 MHz." does NOT mean it will run at that speed on your APU/CPU unless the APU/CPU is also rated to run the RAM at 2133 MHz. Typically most IMCs will run RAM a little higher than the default CPU/RAM frequency and some way higher, (typically Intel).

As an example Deneb CPUs will often run RAM up to 1600 MHz. without issue. Thubans up to 1800 MHz. and FX/Bulldozer up to 2000+ MHz.

As far as perfromance gains in real applications, there is little with DDR3 RAM frequencies above ~1333 MHz on typical AMD and Intel desktop PCs. There are also little if any gains in real apps with tighter latencies when the RAM is above ~1333 MHz. because as the RAM frequency increases the real time for one clock cycle decreases. Thus changing from CAS 9 to CAS 7 @ 1333+ MHz. is less REAL TIME than with the RAM running @ 1066 MHz. Synthetic benches will show gains but they do not transfer to significant gains in real apps as Toms' Hardware, AnandTech and X-Bit Labs and OCN's "damric's" objective application testing has shown.

AMD's Llano is the one application where increase RAM frequency can show significant gains in real apps because the GPU section of the APU benefits from the faster RAM. DDR3 RAM in a typical desktop running at ~1333 MHz. is not a system bottleneck so it doesn't pose a restriction like Llano sees in the GPU section.
Edited by AMD4ME - 5/15/12 at 1:18pm