From the specification page, it looks like it uses a 16 Gb mSATA SSD, which is a separate device from the HDD. It's not a Hybrid SSHD (for example, of the type made by Seagate) which handles the caching internally and the whole caching process is basically invisible to the operating system. What you have, I suspect, uses Intel "Smart Response Technology" which uses a small SSD (up to 64 Gb is supported) to cache frequently accessed system files and programs. Your BIOS may have reference to Intel Smart Response Technology, and it may be possible to disable there.
I have no personal experience of this setup but I would guess caching should also be able to be disabled through the Intel Rapid Storage Technology application in Windows. Just removing the SSD from the system would also presumably disable the caching, while still allowing it to boot from the HDD, but as I said, I've got no first hand experience of using this type of caching setup, so recommend trying to disable it in software and/or BIOS first before removing the SSD physically. I found this summary which gives some explanation of how it works and how to set it up (using the Intel RST software), should you choose to replace the SSD with a new one - https://www.pugetsystems.com/labs/articles/How-it-Works-Intel-SSD-Caching-148/