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Multiple components on one firewire hub ... a problem??

Discussion in 'Converters & Interfaces' started by poprocks, Apr 27, 2005.

  1. poprocks

    poprocks Guest

    My Inspiron has one iLink port and I've added a 3-port firewire pcmcia card. Unfortunately, the iLink port was damaged and the connection can be lost if the cable is nudged.

    Question: If I route both my MOTU and an external HD to the firewire card, will they be fighting for space on the same bus? Is this a problem? How much better (if at all) is the performance if I keep them separated (one on the card, one on the iLink)?

    I haven't gotten conclusive results thru testing yet, so I'm looking for the theoretical answer.


  2. Opus2000

    Opus2000 Distinguished Member

    Apr 7, 2001
    theoretically the bus on a laptop especially will be taxed a little bit more when two devices are on it constantly requesting attention.

    Firewire is robust tho and can handle it....after that it's up to your system and whether it can handle audio data read/write from an external hard drive and record/playback audio through the MOTU at the same time!

    But..only way to know is to keep using it and see if it buckles on ya!

    Let us know either way so there is closure to the post!


  3. poprocks

    poprocks Guest

    Thank you Opus. I will test and report back! Using the iLink and the card separately, I have been recording eight drum tracks simultaneously while cueing to up to four or five scratch tracks. Not even a hiccup. I'll see if anything's different with both MOTU and HD on the card.

  4. OlympicPhil

    OlympicPhil Guest

    Technically, firewire 400 can handle up to 400Mbps and F800 can handle up to 800 Mbps, so whichever you're using, take the value (400 or 800), half it (two devices coming from the hub), and that's the data bandwidth you've got available.

    To work out how many channels you can use before it freaks out, the equation is:
    (bandwidth available) / (sample rate x bit rate)

    so if you're recording at CD quality (44.1k, 16-bit) and your hub's a standard firewire400, (400x1024x1024 bits per second) you can use...

    200x1024x1024 / (44100x16) which works out at about 29 mono channels or 14 stereo channels (or a combination of both).

    Of course, the data bursts aren't purely the audio, there's communication data there too, so knock a few channels off the total to take this into account, and technically you should be able to run at least a 24 track mix at that quality.

    Replace the 44100 with 48000, 88200, 96000, 176400, or 192000 and the 16 with 20 or 24 depending on the sample rate and bit rate you're working at.

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