Linda and others- Thank you for your links and info on the USB - Firewire comparisons. And the OWC link has a $33 Firewire ATA/IDE enclosure. Good find, thanks again. The original poster needed an external HDD to replace the internal one; since performance would be critical for him, Firewire seems to be the way to go. Maybe I didn't express my needs clearly. I'm retired, and my retirement funds (much in Apple stock) haven't done that well this year. I have an extra ATA hard drive, and I looked for the cheapest enclosure I could find. What I need is extra online storage for my music and photos (8 grandkids); as said, I'm retired and speed is less important. I think many people just need more online storage. For most of them, the speed difference is immaterial. Other considerations - cost and com- patibility mainly - are more important, and that may mean USB or it might mean FW. Not to prolong the thread, but some uses run in the background, and drive speed is less important. For example, while an initial backup may take all night, what difference does it make if a regular incremental backup takes a few minutes longer? (I find USB has a few advantages over FW. FW drives have had reliability problems, apparently history but ... . Some USB drives can be powered from the USB port, which is handy for laptops. And the cable is often more flexible than FW cable ;-).) On Dec 19, 2008, Linda <xpressobean at mac.com> wrote: > If you head over to the mac os x support Yahoo group, there are guys > (who > know what they are doing) who have measured all of the interfaces, > and find > USB to be the slowest, no matter the published specs. > > Just my 2¢, > Linda