How to the front Firewire ports affect the rear ports?

Question

How to the front Firewire ports affect the rear ports?

I ave a client that just bought a 2011 MacPro 8 core. They are a few audio interfaces plugged in to a rear Firewire Port (@ FW 400). When he plugs a hard drive in to one of the front firewire ports (@FW 800), the MacPro loses it's connection with the rear.

Did Apple change the front ports to be 'alternate' ports on the same bus- can you only use one at a time?

Or is this a conflict between 400 vs 800? I run both together all the time, and don't have a problem on my older Mac Pro.

Posted on Jul 18, 2011 3:43 PM

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Answer 1

Kappy

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Jul 18, 2011 3:45 PM in response to Lucien Palmer

It's a known issue that some audio devices cause a loss of the use of other Firewire ports or the ability to chain onto the same port.

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Answer 2

Jul 18, 2011 5:53 PM in response to Kappy

Strangely enough, it still works if we chain them through the same port on the back. It's almost like plugging in the drive to the front port 'turns off' the back port.

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Answer 3

Kappy

Level 10

362,023 points

Jul 18, 2011 6:04 PM in response to Lucien Palmer

I remember having the discussion, but cannot remember what the conclusion was as to whether the front and rear ports were off the same chip and bus or if they were independent. Obviously, there's a question about power limits. In other models all the Firewire ports are on the same power line. The USB ports all share their own power line. The power limit for Firewire was nominally 15 watts in total, while the USB ports were limited to a maximum of 500 mA current drain.

But I cannot remember about the Mac Pro since it has both Firewire and USB ports front and back. What you are describing would suggest they are all on the same power line.

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