Some early Intel Macs shipped with just 512MB memory. This was marginal then, and is even more marginal if you have upgraded to Leopard.
If your Intel Mac still has 512MB, this is a cheap and easy way to boost performance. Let me qualify that slightly; easy unless you have a mini. Upgrading memory on a Mac mini is not easy the first time :)
$10 for two 512MB PC2-5300 667MHz DDR2 memory sticks pulled from a MacBook.
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