What tool can I use to see if a hard drive supports Sata3 (6Gb/s)
The SATA 3 interface has been out since 2009 so it is likely most new hard drives support it.
I would use Disk Utility to inspect the drive and it will tell you what model it is then you can get the specs from the manufacturers website.
The issue will be with the motherboard - if it is a older model the chipset may not support the transfer rate.
There is a good article for reference of the SATA standard on Wikipedia.
Maybe something like this
Forgot that hdparm had the option to see Sata1, Sata2, Sata3, NQC and more. But a gui tool would be much better.
This would show what technologies the drive supports (assuming it is the sda):