Probably the best way is to check the BIOS, which will have very detailed information about SATA ports and their respective controller chips. It is also worth looking at the manual for your motherboard to be sure on the exact specifications. However, there are some ways to give an indication of the SATA version used on your motherboard.
One of the most useful tools is hdparm
. You can use it to see how your hard disk is connected by noting which type of SATA ports and the approximate transfer speeds are reported when entering:
sudo hdparm -I /dev/sda
More information is available by looking at man hdparm
or the Ubuntu manpage online.
You can also receive information from the kernel ring buffer by using:
dmesg | grep SATA
which should report the link speed of your SATA boot drive.
Fore more information see: this useful article and also this one.