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SATA Drives: Why Only UDMA 5 And Not 6?

Discussion in 'Windows XP' started by (PeteCresswell), Sep 8, 2010.

  1. (PeteCresswell)

    (PeteCresswell) Flightless Bird

    My Computer | Manage | Device Manager | (view by type) | IDE
    ATA/ATAPI controllers | Secondary IDE Channel | Properties |
    Advanced Settings | Device 0

    In the PC in question, this is a Western Digital Caviar Green
    drive.

    On this one and all the others, "Current Transfer Mode" is "Ultra
    DMA Mode 5", which I understand tb only 100 mbps - whereas 6 is
    133.

    OTOH, the "System" drive is a plain old IDE drive (Western
    Digital WD3200AAJB-00J3A0) hooked into the board's IDE connector
    and it is set to UDMA 6 - or 133 mbps.

    Can anybody elucidate?

    Could it be that the Caviar Greens are inherently slower than the
    WD3200? Doesn't seem logical that what is basically a legacy
    drive would be faster than a SATA drive.... or is it?

    Or is there something else at work?
    --
    PeteCresswell
     
  2. (PeteCresswell)

    (PeteCresswell) Flightless Bird

    Per (PeteCresswell):
    >
    >Could it be that the Caviar Greens are inherently slower than the
    >WD3200? Doesn't seem logical that what is basically a legacy
    >drive would be faster than a SATA drive.... or is it?
    >
    >Or is there something else at work?



    Looking at http://www.pixelbeat.org/speeds.html, I get the
    impression that maybe I've got a mobo issue.

    To wit, maybe my mobo's implementation of SATA connectors is via
    some flavor of IDE rather than the "Serial ATA" shown.

    ??
    --
    PeteCresswell
     
  3. Paul

    Paul Flightless Bird

    (PeteCresswell) wrote:
    > My Computer | Manage | Device Manager | (view by type) | IDE
    > ATA/ATAPI controllers | Secondary IDE Channel | Properties |
    > Advanced Settings | Device 0
    >
    > In the PC in question, this is a Western Digital Caviar Green
    > drive.
    >
    > On this one and all the others, "Current Transfer Mode" is "Ultra
    > DMA Mode 5", which I understand tb only 100 mbps - whereas 6 is
    > 133.
    >
    > OTOH, the "System" drive is a plain old IDE drive (Western
    > Digital WD3200AAJB-00J3A0) hooked into the board's IDE connector
    > and it is set to UDMA 6 - or 133 mbps.
    >
    > Can anybody elucidate?
    >
    > Could it be that the Caviar Greens are inherently slower than the
    > WD3200? Doesn't seem logical that what is basically a legacy
    > drive would be faster than a SATA drive.... or is it?
    >
    > Or is there something else at work?


    I've answered your question, over in the Asus group.

    I can add to that answer a bit.

    Historically, Intel never participated in the UDMA 133 thing.
    Maxtor offered UDMA 133, but Intel steadfastly refused to update
    their chipsets and continued to offer UDMA 100. Some other
    chipset companies added UDMA 133 support, so if you had
    a Maxtor IDE drive and say a VIA chipset, maybe it would
    actually run UDMA6 at 133MB/sec.

    Since Intel showed no interest in UDMA6, it should come as no
    surprise if the "fake" speed offered in the interface, reports
    UDMA5 instead. And it's a fake speed - once you run HDTune benchmark
    and examine the "burst" field in the lower right hand corner of
    the window, it'll tell you the best speed it was able to achieve
    over the SATA cable. The burst test, is effectively testing the
    cache RAM on the hard drive (2MB, 8MB, 16MB, 32MB cache RAM or whatever
    they included). By doing a short transfer to the drive, HDTune
    can time the transfer and see how long it takes, if the transfer
    is stored in the hard drive cache RAM (rather than doing a longer
    transfer that must be stored on the media immediately to work).
    If the program gets it right, then bursting to cache RAM will
    give a feeling for the "true" max transfer rate.

    The very first SATA drives, used a native IDE design, and tacked
    an IDE to SATA bridge chip on it. The SATA cable would be rated
    for 150MB/sec, but the native IDE design would either be limited
    to 100MB/sec or 133MB/sec. If you do the burst test on such an old drive,
    you should be seeing 100 or 133 in the burst window. That would be
    identifying an internal bottleneck inside the drive. As far as I know,
    hard drives now have native SATA controllers bolted to them, so that
    should no longer be an issue. But you may see it on older drives.
    You'd be more likely to see it on a SATA I drive, as any SATA II
    drive should be well past the "bridged" design phase.

    SATA transfer rates can also be bus limited. For example, if you
    were to plug a SIL3132 PCI Express card into a PCI Express x1 slot,
    the slot bandwidth is 250MB/sec max. That is below the SATA II cable
    rate of 300MB/sec. You'd expect the burst test, in that case, to
    report a result consistent with the PCI Express x1 bus limitation.
    So any time you run tests like this, you need to consider the
    architecture you're using, and where the bottlenecks are.

    Paul
     

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