If using for TM, make sure it's at least twice the size you need, any of the left column here...
Thank you for the link. I was under the impression that I should look for a desktop that connects only with USB. I have a firewire on my old external drive and Apple rep told me tp keep it simple. Is that poor advice?
Does your iMac have USB3, or USB2?
Even Firewire400 is generally faster than USB2, & FW800 is way faster.
So we know more about it...
At the Apple Icon at top left>About this Mac, then click on More Info, then click on Hardware> and report this upto but not including the Serial#...
Model Name: iMac
Model Identifier: iMac7,1
Processor Name: Intel Core 2 Duo
Processor Speed: 2.4 GHz
Number Of Processors: 1
Total Number Of Cores: 2
L2 Cache: 4 MB
Memory: 6 GB
Bus Speed: 800 MHz
Boot ROM Version: IM71.007A.B03
SMC Version (system): 1.21f4
SO Sorry not to have stated that my question is about the new iMac that is on order. and want to order a new external. I have fire wire on my old iMac to old external drive and thought that the new set up would be just USB 3.0. Some of the external drives can apparently use either 2.0 or 3.0 but assume that I should update all my USB cords for peripherals to 3.0
OK, USB may work OK on the new iMac, but several problems have been reported... if it were me I think I'd sill go FW800 with a ThunderBolt->FW adapter from Apple.
But if Money isn't a problem, ThunderBolt drives are available & faster by far the USB or FW.
Thank you . This USB/Firewire issue has caused some buyers hesitation. ShoppingI online took me to poor reviews for everything I looked at, although the problems sound MS based rather than Mac. I think my old Firewire is FW 400, it is 5 or maybe even 10 years old. The external drive that it is connected to will be scraped, recently needed disk repair. It was easier to choose the iMac than to settle the issue of getting Time Machine back up to an external drive. Pockets are not so deep after the iMac purchase and speed is not a priority but will do as you suggest. FW800/Thunderbolt adapter and keep 2.0 USB cords for printer/scanner/card reader.