This is a great article that discusses Nehalem memory bandwidth utilization, along with current FSB and DDR3 limitations.
|Chicago (IL) - Intel’s switch to an integrated memory controller with the upcoming Nehalem core will offer enthusiasts to finally take advantage of fast memory devices - which are constrained by the front side bus (FSB) today. The memory controller bandwidth is catching up with performance memory, which means that we should see dramatically improved memory performance one the new CPU arrives.
The performance memory industry is alive and kicking these days, despite the fact that the advantages of higher clock speeds, which currently reach to 2000 MHz, are fading and are virtually non-existent, at least on Intel platforms. The simple reason is that the memory bandwidth is constrained by the FSB, which limits the bandwidth to 8.53 GB/s in a 1066 MHz FSB (266 MHz QDR), to 10.66 GB/s in a 1333 MHz (333 MHz QDR) version and 12.8 GB/s in those rare 1600 GHz (400 MHz QDR) models.
However, dual-channel memory can offer a bandwidth that exceeds what FSB can take: 12.8 GB/s (DDR2-800) to 32 GB/s (DDR3-2000). Even if you buy those ultra-expensive DDR3-2000 devices you won’t see a dramatic increase in performance, at least if you don’t overclock the FSB at the same time. To support that 32 GB/s bandwidth, you would need a CPU capable of running a 4 GHz FSB (1000 QDR).
Intel Nehalem architecture uses 64-bit memory controllers that are directly connected within the CPU silicon, eliminating those "FSB brakes". Expect you bandwidth utilization jumps from current 50-60% to 90%.
Industry sources now indicated that the mainstream Nehalem processor code-named Lynnfield will be able to almost double the memory bandwidth - to about 18.5-20.1 GB/s when DDR3-1333 modules are used.
If you own or plan to buy DDR3 memory, prepare yourself mentally and financially for Nehalem. Intel is currently preparing two different desktop parts: Bloomfield will become the new Core Extreme and feature a triple-DDR3 controller. Using three or six DDR3-1333 modules you should be able to achieve 30 GB/s, while Lynnfield will arrive in Q1 2009 and offer a regular dual-channel DDR3-1333 controller.
So, keep the modules, and wait for their time. It will come.