As noted, SATA doesn't have such. But boot order is usually set by the BIOS and I usually fill the SATA ports from the lowest number to the top number.
I am clueless as to how to set it up to be a slave - the markings are different on the bottom; left to right are to dots for 3 and the right one has a dot over a square. Both are 500 GB HDD and I had it in the computer and they were at one time both active. Computer is a Compaq, Model #: CQ5826, Product #: QX350AA#ABA, and it has Windows 7 Home Premium. I had hoped to use it as a backup for the main 500 GB HDD. Originally, I had it installed w/o a pin connector in it, later put a pin connector on the last one. I had used HP Recovery (D:), deleted that and put D: Recovery on the new drive. It did back up everything but it was an .iso image. I had to delete both with www.killdisk.com. Darrell