Confused: FW 400 and my 2.66 Quad Xeon

Discussion in 'Mac Pro' started by prairiefire, Feb 23, 2010.

  1. prairiefire macrumors member

    Joined:
    Jun 8, 2007
    #1
    I'm trying to figure out how to use my iSight and my FW400 drives with my computer which has only FW 800 ports.

    I've read all of the posts on the use of adaptors and cables to go from the computers FW800 ports on the front and rear of the computer and allow the use of the FW 400 devices.

    From what I understand, because the computer has but one FW bus, if a FW400 device is connected to it, it dumbs down the FW800 devices to run at 400. And, it does so with both the rear and front FW800 ports. Am I right, so far?

    I also understand that if one puts in an expansion card to create FW400 outlets, it does not slow down anything being run at FW800 from the front or rear FW800 ports? Is that right, too? (If so, just curious. Does the card create a new "bus"?)

    Now the wrinkle.

    I've got an Apple Cinema HD display hooked to the computer. There is a FW 400 male fitting coming off of the "multi-cable" that plugs into the computer. Until today, it was not connected to anything. Today, I put that FW 400 male into a powered FW400 hub, and then plugged my iSight and some FW400 drives into that hub and all are working well.

    Here's the Question: Will this set up slow down my FW800 devices to FW400? Or, is this a separate source of FW400 as would be an expansion card, so that it does not affect the FW800 ports on the front and rear of the computer?

    I hope I've expressed this clearly.

    Thanks for all the support I get here.

    sjh
     
  2. Techhie macrumors 65816

    Techhie

    Joined:
    Dec 7, 2008
    Location:
    The hub of stupidity
    #2
    The firewire ports are independent, and any one device connected to one cannot effect the others.

    The "new bus" being created is actually using the bandwidth of the PCIe slots, and also has no effect on the rest of the system.

    I'm curious, does the FW400 hub run from a FW800 port attached to the computer? Regardless, because the hub can only draw data from one independent port, each subsequent device using the hub will be throttled according to how much bandwidth is currently being used. Anything else that is plugged directly into the machine will not be effected by hub operation.
     
  3. prairiefire thread starter macrumors member

    Joined:
    Jun 8, 2007
    #3
    Ah, you've cleared up some of it! Thanks.

    The firewire ports are independent, and any one device connected to one cannot effect the others.

    From reading a thread and some posts in this forum, I misunderstood the nature of the 4 FW800 ports on my computer. Here's the thread that had me confused. I took it to mean that putting a FW800 to 400 adaptor on one of the FW800 ports dumbed down all of the ports to FW400.

    Here's the url of that thread: http://forums.macrumors.com/showthread.php?t=677798&highlight=fw+400

    Now, I'm wondering if what they were saying was that if you use a FW800 device to connect a FW400, the 800 will slow down to 400.

    Yet, they still leave the impression that there is "one FW800 bus" (whatever that means, and any connection of a FW400 to it will slow everything down.

    What's particularly confusing is their finding that hooking something to the rear port slowed down the front port -- at least that's what I think they are saying. Are they?


    The "new bus" being created is actually using the bandwidth of the PCIe slots, and also has no effect on the rest of the system.



    I'm curious, does the FW400 hub run from a FW800 port attached to the computer? Regardless, because the hub can only draw data from one independent port, each subsequent device using the hub will be throttled according to how much bandwidth is currently being used. Anything else that is plugged directly into the machine will not be effected by hub operation.

    And, this is exactly what I wanted to know. So, if I use one of my four FW800's, with a Belkin 800 to 400 cable to the 400 hub, it will not affect all of the FW800 devices connected to my other 3 FW800 ports? (Of course, everything hooked up to the hub will be at FW400 because it is a FW400 hub and offers not connections for FW800.)


    Thank you so much for helping me. I'd really like your take on the thread at the url I included.

    Thanks, again.

    Steve
     
  4. alphaod macrumors Core

    alphaod

    Joined:
    Feb 9, 2008
    Location:
    NYC
    #4
    Only if you daisy-chain a Firewire 400 device on the same bus with other Firewire 800 devices, the bus will they slow down; if you use different ports then one cannot affect another.
     
  5. rickvanr macrumors 68040

    rickvanr

    Joined:
    Apr 10, 2002
    Location:
    Brockville
    #5
    Yeah you just need something like this;

    Moshi 800 to 400 Adapter

    I've been meaning to get one, but I'm waiting until there is something else I need from the Apple Store so I don't get dinged with a shipping charge
     
  6. prairiefire thread starter macrumors member

    Joined:
    Jun 8, 2007
    #6
    Thanks to all for the answers.

    I know understand how to do this correctly.

    Best,

    Steve
     
  7. DualShock macrumors 6502

    Joined:
    Jun 29, 2008
    #7

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