I think you are mixing two things up. Samsung's Rapid mode uses a chunk of memory as a cache for your SSD. Intel's Smart Response uses a SSD as a cache for hard drives or hard drive arrays.
I don't think you are going to get Intel's SRT to work with an OS installed on the SSD. You are pretty much going to have to wipe that drive. Then you can use RST to accelerate your hard drives. With some jiggery-pokery and diskpart, you will then be able to use the remaining space on the SSD, but I'm not sure if that will get you a bootable OS drive running along with Intel's SRT.