Because I would like to OC.
I want 8GB but 4GB (2x2GB) is really expensive at ddr2-667, and Kingston is the only manufacturer I have seen that has that kind of memory out right now thats unbuffered. It sells for over $1300. Thats ridiculous.
Mushkin currently makes some inexpensive 2GB sticks, but they only go up to ddr2-533 and that will make it hard to OC. They sell for about $115 a GB so its actually rather inexpensive. But now Im stuck with one of two options.
1.) Get 8GB - Much improved multitasking. All apps run at max. No OC
2.) Get 4GB - Better performance. Each indivual app will be able to render things faster, thanks to OC.
With the RAM sensitive Apps I use, adding more RAM increases performance, but so does increasing CPU frequency. So I should see just about the same performance increase when multitasking. But when Im using just one or two, then Ill probably only benefit from the OC.
I have seen benchmarks and I am not interested in FB DIMM. Xeon shot himself in the foot in the workstation market with the adoption of FBDIMM.