I've seen a lot of questions concerning SATA III (II), and what Mac has what. This little tutorial should help you determine what you have in the HD Bay as well as the Optibay. Mods, if this info is somewhere else, please move as appropriate with my apologies. Step 1. Click on the Apple logo and select "About This Mac" Step 2. Click "More Info" Step 3. Click "System Report" Step 4. In the left panel, highlight "Serial-ATA" Step 5. Select the controller with the triangle next to it (see pic below) Now look at the Link Speed. If 6 Gigabit is displayed you have SATA III. If 3 Gigabit it's SATA II. The "Negotiated Link Speed" is what connection you currently have. In the picture provided, you can see the Link Speed is 6 Gigabit while the Negotiated Speed is 1.5. What this means, is the DVD drive is standard SATA. Therefore, while the controller is SATA III (link speed), it can only achieve a negotiated link speed of 1.5 because the DVD limits it. If a SATA III SSD were installed in place of the DVD (Obtibay), the negotiated link speed would change to 6 gigabit. I hope this helps alleviate some confusion.