so if i coonect my hdd to sata 6 will it improve performance or not?
you can connect the hdd to the sata 6gbps port, the ports are backwards compabitle. but don't expect any performance increase because mechanical hdds can't even saturate regular sata 3gbps.
you could test with a benchmark or try to copy files from one partition to another and monitor the speed.
one more thing, does your dh67cl motherboard have b3 rev.? just checking.