[DMcCunney]

Originally Posted by Gregg Bell

So you're stuck with whatever memory type you have then because of the shape, right? So DDR2 has a different shape than DDR3?

Yes.

There's no sense of "I'm going to speed this computer using DDR2 by getting rid of the DDR2 and using DDR3"?

Correct. The machine can't actually use DDR3. And while there are different speeds of RAM within DD2, DDR3, etc, there's no point in buying faster RAM than the machine can use. The RAM just needs to be fast enough.

The first way to boost performance on an existing machine is to add more RAM. As mentioned, machines are I/O bound, and spend most time in a wait state waiting for I/O to occur. Anything that reduces the need to access disk cuts I/O time, and more RAM allows better caching and less disk access.

The second way to boost performance is to move to a solid state drive. Those are an order of magnitude faster than standard hard drives, so stuff that does access the disk happens a lot quicker. (Note that this speeds up booting and program loading. It makes no difference in performance once things are loaded and running.)

The third way is to get a new machine with a faster processor, but most cases can be handled by steps one and two.

I ran

dmidecode

and got "permission denied." It didn't ask for sudo or anything.

It won't. Try running it from a terminal as "sudo dmidecode".
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Dennis