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Mixing Firewire 800 and 400 on an iMac?

228 Views 3 Replies Latest reply: May 6, 2012 8:00 PM by jsd2 RSS
Alfredo Jahn Level 3 Level 3 (805 points)
Currently Being Moderated
May 6, 2012 6:52 PM

I have 2 external FW 400 drives on my late 2011 iMac. I use an 800 to 400 adapter. I've been thinking of getting a new external drive from OWC. The have both 400 and 800. The 800 case has 2 800 connectors and one 400. Does it make sense to mix? Will they all run at the slowest in the chain?


I was thinking of connecting the 800 directly to the iMac using the built-in 800 connection. Then chaining from there using the 400 connection to the other existing 400 external drives. Will I actually get 800 speed on the first drive?



iMac 3.06 GHz Intel Core i3, Mac OS X (10.6.8), 12GB RAM, iPhone 3gs, iPhone 4s
  • Allan Eckert Level 8 Level 8 (39,335 points)
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    May 6, 2012 6:56 PM (in response to Alfredo Jahn)

    They will run at the speed of the slowest in the chain.



  • jsd2 Level 5 Level 5 (6,200 points)
    Currently Being Moderated
    May 6, 2012 8:00 PM (in response to Alfredo Jahn)

    I have a mixed group of external drives, and just bought a new OWC Mercury quad interface drive.


    The user manual that came with it says:


    Note: If you are using FireWire 800 and add a FireWire 400 device to the chain, all devices will be reduced to FireWire 400 performance



    I tested this myself, which confirmed it. I set up the following chain,  with the first 2 drives connected by FW800, and with a FW400 drive either connected or not connected at the end:


    HD  ----800-----DRIVE1------800------DRIVE2-------400-------DRIVE3


    I booted from my HD and timed the copying of a large file from DRIVE1 to DRIVE2. Although the FW400 drive was at the end of the chain and was never involved in the copying, just having it attached immediately reduced the speed of the file copy from Drive1 to Drive2. The actual speed reduction in practice was about 40%, not 50%.


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