If your composition uses a lot of layers of video and large JPEG's, it's going to have to use your RAM like crazy. If it runs out of RAM, it's going to have to start swapping things to the hard drives and the processors are going to be waiting for data to arrive. So it will speed up some renders if you have more RAM.
If your composition is a bunch of 3d solids and text with several lights and heavy depth of field, you're going to be waiting for your processors to chug through all those calculations and your RAM is going to go fairly unused.
Does that make sense?
I don't know about how hyperthreading or multithreading goes as far as RAM usage. I don't have enough equipment here with enough down time to test that. However, I think I have something that may help: [link] The resources at that link and the forum thread it links to should help you as you figure out what's best.
- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')
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