A7N8X Deluxe...Asus says it DOES support 150Mhz with it's onboard serial ATA..are they lying?

Discussion in 'Asus' started by John Q. Public, Aug 31, 2004.

  1. A7N8X Deluxe...Asus says it DOES support 150Mhz with it's onboard
    serial ATA. I've heard that the serial ATA on the A7N8X Deluxe runs
    thru the PCI, and is therefore limited to 133....but Asus says no to

    John Q. Public, Aug 31, 2004
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  2. John Q. Public

    Damien Guest

    The FAQ states is spports 150MB/s... between the SATA controller and the
    hard drive. PCI is still clocked as usual.

    Damien, Aug 31, 2004
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  3. John Q. Public

    Paul Guest

    Sometimes I don't know why Asus bothers with the FAQ page...

    SATA performance has the following limits:

    1) Media head rate - Raptor is 70MB/sec and is the fastest I know of.
    2) Drive can have a RAM cache. Depending on where this sits (before
    or after bridge), it can absorb the full data rate for short
    3) Drive uses IDE/SATA bridge chip - this is limited to 100MB/sec
    or 133MB/sec. I don't know if there are any native hard drives yet
    or not.
    4) Cable rate is 150MB/sec and this is fixed. The cable actually
    runs at 1500Mbits/sec, and is 8B10B coded. The coding reduces the
    usable data rate to 1500*(8/10) = 1200Mbits/sec and this is the
    stated 150MB/sec. I haven't read the whole spec, but it is
    possible fewer symbols per second could be sent if flag
    symbols (like JK or K28.5 are sent) are used to take the place
    of data.
    5) The SIL3112 has FIFO buffers inside the chip, which makes it
    possible for the chip to absorb data at full speed (150MB/sec)
    for very short intervals, from the SATA cable. I don't know how
    flow control is achieved or whether flow control results from
    limiting the size of data chunks used for transfers.
    6) The PCI bus has a theoretical burst rate of 133MB/sec for the
    32bit 33MHz version of PCI. When using reasonably short data
    bursts on the bus, about 100MB/sec will be achieved. But the
    SIL3112 datasheet says the chip can be clocked at 33MHz or
    66MHz. It is unlikely a desktop motherboard would have something
    faster than 32bit 33MHz for the PCI bus, so the 66MHz option is
    extremely unlikely. (I would need Nvidia documentation to be
    sure and they don't give it out.)

    After all that mumbo-jumbo, most people will find bursting of
    less than 100MB/sec for short intervals, is their limit. This
    limit can be in several places, as stated above.

    Higher than 100MB/sec has been achieved. Someone benched the
    Intel SATA RAID on the ICH5R, and because the bus connection
    inside the ICH5R is 266MB/sec, faster than 100MB/sec is
    possible (with two Raptors in RAID mode).

    I've also read comments recently from someone who has compared
    the same IDE drive with and without a SATA adapter connected to
    it. He finds the SATA way is slower, and this could be due to
    the protocol overhead for sending commands to the drive. But until
    you have seen several people try this experiment with different
    brands of drives and PATA/SATA adapters, don't take this
    suggestion as gospel.

    Paul, Aug 31, 2004
  4. John Q. Public

    Andrew Guest

    SATA has a maximum speed of 150MB/s
    PCI has a maximum spped of 133MB/s

    SATA has a MHz value of 1500
    PCI has a Mhz value of 33

    it is all to do with the number of bits moved in each cycle.

    for SATA, this is 1
    for PCI, this is 32.

    I currently ignore PCI-X or similar as they are not common. For
    reference, the better PCI found on server boards is 66Mhz, 64bit per
    cycle for a total of 533MB/s

    and if you would like, think back to the old ISA format, 8Mhz and
    16bits (if I recall correctly).

    These speed limits are are expected to be around for along time, at
    least until the newer PCI standard comes more common

    Andrew, Sep 1, 2004
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