The chip density thing should only be an issue if you have an older computer.
If I remember what I read on it correctly, some older computers will not recognize newer manufactured memory due to increased chip density during manufacture. There are brands out there that this is not a problem with but I'm at a loss to tell you which ones.
I believe the older Dells were one of the brands of computers mentioned that were affected by this problem.
is a link 4 u.
Hope this helps a little.