can I just buy a usb c cable for a external?

Fishrrman

macrumors Core
Feb 20, 2009
19,459
6,758
"will the older/slower harddrive transfer at usb-c type speeds or will it still be usb 3.0 speed? Basically, is the speed determined by the hard drive or the cable?"

Actually, by both.
Think of the old saying that "a chain is only as strong as its weakest link".

Same goes for a USB "chain".
A "faster" connecting cable can't speed up a slow drive.
A fast drive can be hamstrung by a connecting cable that isn't up to the job.

Even a USBc drive may operate at only gen1 speeds (depends on the components inside).
 
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