USB versus Firewire

I am kind of annoyed by this Macworld UK article: USB 2.0 hard drives
The author, Rosemary Haworth, says of Firewire support: "You’ll pay more for this feature, and many people won’t need it, given the advantages of USB 2.0 over the dreadfully slow USB 1.1 standard.".
I think you've done some people a disservice Rosemary, by not telling them about the advantages of Firewire, which are more subtle than just bus speed.

When reading or writing to a Firewire drive you'll find that the CPU is very lightly loaded compared with USB. This is because the CPU is heavily involved in USB data transfers, but with Firewire it is different. The Firewire disks can directly transfer data into memory without CPU supervision (the CPU asks for the data transfer and then is free to do other work while the Firewire hardware takes care of the transfer - at the end of the transfer the CPU is notified).

Who cares you might ask ? Well, here's an example of where Firewire is important:

You are an engineer or Product Manager and you use VMWare Fusion to run VM's of Windows as part of a customer demo. Have you ever been embarrassed by how long the VM takes to load or how sluggish it is to run from your laptop. Well, buy an external Firewire drive and put your VMs on it. Since data transfers from Firewire use little CPU, the CPU is free to run the VM - and you get the advantage of two disks (your main one provides the OS and Applications, and the VM comes from the external disk - you effectively have twice the hard disk speed).

In a nut shell, USB is great so long as you don't really need all of your CPU at the same time as you need data from the USB disk. Where-as Firewire leaves most of your CPU alone - for productive use.

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