That's a much better question.
To answer: As imgod2u said, you can add that no, usually 333MHZ on 266MHZ bus is not too helping, if at all. In rare cases like the Pentium 4, which eats any bandwidth you give it, it will give some improvement, but on Athlons, you need a higher bus as well!
You can buy DDR333 so in the future, should you buy AMD processors, you can keep it.
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