17"MBP- Are there multiple data channels or are FW800, USB2, & expresscard shared?

Discussion in 'MacBook Pro' started by rawdawg, Mar 11, 2010.

  1. rawdawg macrumors 6502

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    Jan 7, 2009
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    Brooklyn
    #1
    I have the newest 17" MBP (which kept the ExpressCard slot - yeessss!)

    I have the best eSATA card available for it, Sonnet Tempo Pro, which I'm using with my RAID 0 from OWC. I render and export huge files on it. Right now I'm transcoding a 200Gb uncompressed video file to ProRes.

    I was wondering if adding another external hard drive would speed this up? The Sonnet eSata card has two eSata connections but adding another eSATA hard drive would effectively reduce the throughput there in half.

    If I get a FW800 would I then have the benefit of full eSATA speed (that my card is capable of, ~180MBps by the way) AND full speed the FW800 channel has? Or do they share channels somewhere down the line? (ie. are these separate connection possibilities independent data channels?)

    I left out USB2.0 because it's obviously slower, but what about that too?
     
  2. psingh01 macrumors 65816

    Joined:
    Apr 19, 2004
    #2
    I haven't seen an schematics for a MBP but each type of port would have it's own controller. Definitely the express card slot (which would be like a PCI slot on a desktop) and the FW/USB would be on different channels. It's possible that the FW/USB are handled by the same controller, but they could be separate. So yes, you should get benefit of using these separate ports.

    Are data channels shared at some point? Yes...once they get to the CPU :D This likely only talks to one I/O controller which talks to the other controllers.
     
  3. m85476585 macrumors 65816

    Joined:
    Feb 26, 2008
    #3
    Not exactly the chipset in MBPs, but it's close enough.
    http://www.xbitlabs.com/images/mainboards/ga-p35-ds3r/block_diagram.jpg

    The expresscard slot is a USB port and a PCI-e 1x lane. The Firewire chip is likely on a PCI-e lane.The USB ports are built into the chipset directly.

    You might run into problems if one disk is waiting on another one, though, in which case both disks will probably run at the speed of the slowest disk.

    Edit: updated diagram for Core i5/i7 MBPs:
    http://benchmarkreviews.com/images/...el_dp55kg/intel_p55_chipset_block_diagram.png
     
  4. rawdawg thread starter macrumors 6502

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    Brooklyn
    #4
    Thanks for those schematics
    The limit of my RAID 0 is ~180MBps but that's on large file reads. Definitely faster than FW800. But if my footage was on the RAID and I am exporting to that same RAID, I imagine then since it would be reading and writing that the same drive then speed would suffer...? Or does it read a large chunk to memory and then write a large chunck as needed. Listening to the RAID I hear it clicking away which concerns me that speed is wasted reading and writing at the same time not to mention wear/tear.

    Would using two separate drives on different data channels I thought could speed it up.

    I really don't know though. Any pro's out there have an opinion? (My RAID0 is a simple 2 drive hardware Mercury Al Pro from OWC)
     
  5. m85476585 macrumors 65816

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    Feb 26, 2008
    #5
    In that case you might be able to speed it up using two separate disks. Look at the disk speed graph in Activity Monitor and see how close to the max speed you are getting.
     
  6. t0mat0 macrumors 603

    t0mat0

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    #6
    If the ExpressCars is USB - is there any point getting a ExpressCard USB3 card then?
     
  7. Denarius macrumors 6502a

    Denarius

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    #7
    I won't say it for certain, but I would have thought that bottlenecking expresscard to USB 2.0 would be spectacularly stupid design.
     
  8. m85476585 macrumors 65816

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    Feb 26, 2008
    #8
    The expresscard port offers USB and PCI-express. I would certainly hope all but the cheapest USB3 expresscards use the PCI-express interface, not USB. The USB interface is often used by card readers, cheap USB cards (hubs, basically), and cheap SSDs.
     
  9. rawdawg thread starter macrumors 6502

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    #9
    Not sure why I didn't think of that. Actually I didn't realize Activity Monitor did that.:eek:

    Thanks m85476585, this should tell me what I need to know!
     

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