Can a single memory be installed?

Yes with no negative impact or ramification other than what you're doing. As long as you're not using RAM hungry apps (Video, Photo, gaming etc) you'd never see the difference. It doesn't take much RAM for email, word processing or web browsing.

If you loaded 8GB in each side you'd have the Max RAM... more RAM - increased performance Mac OS X loves RAM. Short of buying a new Mac or a processor upgrade, adding RAM is the best way to improve Mac OS X performance. Install the maximum amount of RAM that your Mac will accept and your budget will allow.

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