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Firewire vs. USB

September 10, 2009 2 comments

The battle between Firewire (A.K.A. IEEE 1394, iLink) and USB rages on.

i switch

It’s well known that although USB 2.0 shows a higher speed on paper (480Mbps vs. 400Mbps) than Firewire, due to inefficiencies in USB protocol and the fact that USB requires the host to manage the transfer of data, Firewire is in actual fact faster on the whole.

The reason is cited as being not just the efficient, real-time, streaming oriented protocol but the Firewire controller itself, which manages much of the dirty work when it comes to data transfer, offloading the stress of controlling real-time, high speed data from the motherboard/CPU onto the device.

This offers two main benefits:

  1. The host CPU or controller has less work to do and can focus on other, more important stuff, meaning the attached host will feel more responsive and less stressed under heavy load.
  2. Because major data flow control is performed on the device itself, wasteful, detailed control data does not have to flow back and forth between the device and the host, leading to less wastage and latency.

…and two main drawbacks:

  1. The controller is relatively complex and thus expensive.
  2. The controller’s complexity can lead to difficult to diagnose compatibility issues.

Which leads to my main issue.

My Logitec MA-16FU2/WM external firewire and USB dvd burner regularly fails to mount disks on my Mac, while connected by Firewire but performs flawlessly with USB.

Basically, no disks inserted will mount at all under Snow Leopard.

Indeed “about this mac/more info…” shows no sign of any volume in this drive, whether it’s directly connected to the mini or via the firewire hub of the Princeton PHD-MM160IUH.

Moreover a second firewire / USB device will often fail to remount over firewire if I shut it down or disconnect it. Again, it works flawlessly over USB. Moreover, it even works with Firewire when connected to my Windows PC!

Go figure!

I’ve tried:

sudo kextunload
/System/Library/Extensions/IOFireWireFamily.kext/Contents/PlugIns/AppleFWOHCI.kext/

and:

sudo kextload /System/Library/Extensions/IOFireWireFamily.kext/Contents/PlugIns/AppleFWOHCI.kext/

but the external drives just shut down and restart, still without mounting the volumes.

No joy.

It’s really ironic that the Mac has worse support for firewire than Windows, especially since Apple were one of the founders of the specification.

basically, despite the ‘so-called’ superiority Firewire, I can only get my job done reliably with USB… sigh.