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Article:
  Road Testing the PowerBook Ti 667
Subject:   Hard Disk RPM
Date:   2001-11-27 01:56:17
From:   salamander_
Remember that laptop hard disks are 2.5" in diameter, whereas desktop hard disks are 3.5". Since circumference is proportional to diameter, you only need to spin the smaller disk at 2.5/3.5, or 72% the speed of the faster disk to get the data passing beneath the heads at the same speed. You can therefore expect 5400rpm 2.5" drives to to have better performance on average than 7200rpm 3.5" drives of the same capacity.


Of course this ignores many issues such as the number of platters, the chipset, the bus bandwidth, caching and so on. But you should keep it in mind when making RPM comparisons between disks of different sizes.
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  • Derrick Story photo Hard Disk RPM
    2001-11-27 07:42:55  Derrick Story | O'Reilly AuthorO'Reilly Blogger [View]

    Excellent point! If you're correct, and I'm guessing that you are, then that's a pretty strong argument for the upgrade to the 5400 rpm disk for power users.

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