SATA SSD to ATAPI bridge in lower optical bay

Discussion in 'Mac Pro' started by NoManIsland, Dec 25, 2010.

  1. NoManIsland, Dec 25, 2010
    Last edited: Dec 25, 2010

    NoManIsland macrumors regular

    Joined:
    Feb 17, 2010
    #1
    I have a 2008 Mac Pro (currently ko - see "Screwed up" thread), and I have OWC's Multimount mounting solution to put two SSDs in the lower optical bay: http://eshop.macsales.com/item/Other%20World%20Computing/MM352A52MP8/
    I also have a Pioneer Blue-ray writer in the upper optical bay that I have connected to the ATAPI connection in the optical bay via an adapter:
    http://www.newegg.com/Product/Product.aspx?Item=N82E16812240012
    I have the two SSDs hooked up with SATA cables to the ODD SATA ports on the logic board, with a power splitter/adapter dividing the second optical bay power lead. I've been thinking of adding a third SSD to the lower optical bay using the ATAPI connection designed for the second optical drive (through the same type of adapter), and a SATA power splitter coming off one of the leads that power the existing two SSDs.

    What I am wondering is if this could cause any power issues, and whether the ATAPI connection is going to be bottlenecking the SSD badly.
     
  2. SmilesLots macrumors regular

    SmilesLots

    Joined:
    Apr 30, 2010
    Location:
    SW Virginia
    #2
    SSDs use so little power that I think you could probably run 20 of them before you would have any power problems, if any at all. But speed through Atapi is definitely going to limit SSD performance IMHO. If you can, install a pci-x to sata/esata card, and you'll have your speed. You can get one for under $10.
     
  3. Transporteur macrumors 68030

    Joined:
    Nov 30, 2008
    Location:
    UK
    #3
    PATA = 133MB/s (~100MB/s real life performance)
    SATA = 300MB/s (~275MB/s real life performance)

    Apparently the performance hit will be huge. Definitely not the way to go.
    As already mentioned, a cheap SIL3132 based SATA card will give you the full performance. They won't be bootable, though.
     
  4. NoManIsland thread starter macrumors regular

    Joined:
    Feb 17, 2010
    #4
    Thanks for the info, I suspected as much. It does bring up a question, however: my Blue-ray drive is a 12x writer, do you think that it is being bottlenecked as well? I'm really hoping to keep it hooked up to the ATAPI connection as I need the two ODD SATA ports for those two SSDs and don't want to fill a PCIe slot with a SATA card if I can avoid it.
     
  5. Transporteur macrumors 68030

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    Nov 30, 2008
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    UK
    #5
    12x BluRay means a transfer rate of 54MB/s, so IDE is plenty fast for that.
     
  6. NoManIsland thread starter macrumors regular

    Joined:
    Feb 17, 2010
    #6
    That's great to hear, thanks. About the free ATAPI port in the optical bay, I understand that it is too slow for an SSD, but would it bottleneck a 2.5" SATA conventional HDD?
     
  7. Transporteur macrumors 68030

    Joined:
    Nov 30, 2008
    Location:
    UK
    #7
    Nope. Today's 2.5" drives don't reach speeds of 100MB/s, so you're good to go.
     
  8. jdiamond macrumors 6502

    Joined:
    Dec 17, 2008
    #8
    Atapi speeds...

    Although ATAPI could be viewed as a class of PATA, it was not designed for hard drive use, and I don't believe it ever exceeded 33 MB/second, with most still at 16MB/sec. When I asked my local Apple repair about it, he said that the ATAPI in most Macs is definitely not faster than 33MB/sec.

    If you find differently, please let me know.
     

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