Help needed with optical bay of early 2008 macbook 2.4 GHz white

So I've had an early 2008 macbook (white) with 2.4 GHz and I'm considering replacing the HDD with an SSD, however, I'm limited to only 1.5 GB/S with SATA and I've heard that replacing the SSD in the optical bay will yield better results because of higher reading speed. I just want to know what the reading speed of the optical bay is.

Thank you in advance