A hard drive (3.0 Gb/s) I have recently bought just came, without a SATA cable. I have a 6.0 Gb/s capable SATA cable sitting around. Are these 6.0 Gb/s cables backwards compatible? If I use it, would I have to plug it into the 6.0 enabled port on the mobo or can I just use the normal SATA ports?
They are backwards compatible. And you can plug it into any SATA port you like.