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The Mac Pro supports SATA2 but it is backward compatible with SATA 1. And really you don't get much if any boost from SATA2. The drives can't even reach the speeds of SATA 1.

EDIT: that drives is SATA 2 anyway....3.0 Gb/s almost means SATA 2 vs 1.5 Gb/s is SATA 1
 
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