It's now time to look at memory controller performance. AMD was the first to implement an integrated memory controller, but lately its memory controller design had troubles keeping pace with Intel ones. Will Bulldozer change anything? Scott Wasson at techreport.com always did a wonderful job in examining new processors, and he use the industry standard STREAM benchmark to look at memory bandwidth.
As you can see, the bulldozer-based FX-8150 show exceptional performance here, beating the mighty Sandry bridge also. Sure, there are other tests with different memory access patters where Sandry bridge remain superior, but this is not the key question.
The point is that Bulldozer memory performance are at least very competitive and way higher than PhenomII's one. So, Bulldozer's memory controller is a strong point of the new architecture. Any slowdown can not be attributed to it.