I'm Stumped - 1.5G speed with a 6G SSD via eSATA?

Discussion in 'Mac Pro' started by khollister, Nov 23, 2011.

  1. khollister, Nov 23, 2011
    Last edited: Nov 23, 2011

    khollister macrumors 6502a


    Feb 1, 2003
    Orlando, FL
    I was testing a Crucial M4 6G SSD and I dropped it in a Mercury Elite AL Pro Mini enclosure and connected it via eSATA to an OWC Maxpower eSATA card (the non-RAID one). I only get about 125 MBs read.

    If I move the M4 internal, I get the expected 250-260 MBs read (3G channel).

    If I move my 3G OWC SSD to the external enclosure, I get the expected 250 MBs speed.

    Is there some compatibility issue with 6G devices and 3G eSATA controllers or bridge chips? THe eSATA card is rated at 6G, but the bridge in the external is only spec'd at 300 MBs (3G).

    What the hell is going on?
  2. michael_aos macrumors 6502

    Jan 26, 2004
    I've been having a bunch of issues with OWC eSATA only linking @ 1.5G.

    Curious if anyone else has seen this?
  3. kwarwick43 macrumors member

    Aug 11, 2008
    I've had similar issues, which I originally assumed was a problem with the card. I was using it with a Thermaltake USB 2.0/eSATA dock as well as a couple of different brands of external eSATA drives... none of them would negotiate above 1.5Gb even though the drives were 3G capable.

    Recently I swapped out the Thermaltake dock with a Vantec USB 3.0/eSATA dock and was very surprised to see that it was negotiating 3G connections. First time I'd seen this card do 3G (even though it should be able to do up to 6G).

    Why the model of eSATA dock should mater is beyond me, as I understand SATA to eSATA is just a passive connector change and shouldn't be able to mess with SATA speed negotiation.
  4. JQuick macrumors member

    Feb 2, 2014
    Is port multiplication circuitry also in the mix?

    I believe that in most port multiplier implementations the SATA interface chip itself talks to the host at 6Gb/s then fans out to 4 lanes of 1.5Gb/s.

    Some newer controllers use Command based, or FIS-based (Frame Information Structure) designs to work around this problem, but I do not know how much more expensive they are or how much the drivers differ.

    see this explanation of what you are likely seeing:

    The race to the bottom in technology margins and prices often leads to this situation, you can have inexpensive or well-designed (choose 1).
  5. kwarwick43 macrumors member

    Aug 11, 2008
  6. slughead macrumors 68040


    Apr 28, 2004
  7. kwarwick43 macrumors member

    Aug 11, 2008
    8 core 2008 (3,1). And yes, I had it installed in slot #2 which is one of the PCIE 2.0 slots. I have since moved it to slot 3 (both my 2.0 slots are used with other cards that need the bandwidth), but the negotiation issue didn't change. Only now that I've changed to the Vantec eSATA dock does it negotiate properly.

Share This Page