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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > Mac Desktops > '08 iMac FW 400/800 / USB Speed

'08 iMac FW 400/800 / USB Speed
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Fresh-Faced Recruit
Join Date: Oct 2004
Location: Central PA
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Aug 3, 2008, 02:59 PM
Are some or all of the Firewire and USB ports on the 2008 iMac on the same bus? Wondering about the possibility of striping across the two FW800 ports, possibly others. Not enough drives to test myself at the moment.
Big Mac
Clinically Insane
Join Date: Oct 2000
Location: Los Angeles
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Aug 3, 2008, 03:48 PM
It looks like they're still on one bus to the south bridge:


"The natural progress of things is for liberty to yield and government to gain ground." TJ
Posting Junkie
Join Date: Oct 2005
Location: Houston, TX
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Aug 3, 2008, 03:53 PM
Note that one of the Firewire ports is 800Mbps while the other is 400. The Firewire ports share a 250MBps link from the Firewire controller to the southbridge, which substantially exceeds the combined bandwidth. The USB ports each have their own channel to the USB controller.
Posting Junkie
Join Date: Nov 2000
Location: in front of my Mac
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Aug 4, 2008, 05:30 AM
FW does DMA. USB doesn't. Hence the different interfacing with the rest of the chipset.
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