100 times Faster HDD speeds. Is this real? Does Primocache application really work?

To add to @r2d3’s answer, I’ve ran some tests on my own RAMDisk.

The software I’ve used is ImDisk, on a 512MB FAT drive (mounted as the R:/ drive).
My system has 2x8GB Kingston KHX3000C15D4/8GX (3000MT/s), on a MSI B450 Tomahawk Max motherboard and an AMD Ryzen 5 3600 CPU.
The RAM usage was about 47-48% at the time of testing.

Doing a 256MiB test, with CrystalDiskMark 8.0.1, I got these results:

Without the use of that software, I (kinda) replicated the results you’ve shown.

In conclusion: that software is using a ramdisk as cache, or some RAM caching.

Your HDD won’t magically start working at over 9000MB/s, specially a SATA3 HDD.
And since you’ve specified a read/write speed of 100MB/s, my guess is that you have a 5400RPM HDD or an half-full HDD.

In fact, quoting the website:

Mục lục bài viết

Load Apps and Data Faster

Effectively cache your frequently used applications, documents and other data into faster storage devices, accessing them at up to RAM-like or SSD-like speeds. Make your computer more responsive for creating, gaming and producing, with less boot and load times.

Accelerate Writing

Complete write requests very quickly by temporarily storing incoming data into RAM or SSD storage first and writing them back to target disks later. Enable your computer to handle heavy or stream write IOs, while reducing writes and wear on disks.

It describes exactly what it does, so, it isn’t really a scam, as some users have been describing it as.
It has marketing fluff all over it, as many products do.

It is a pricey software, and you might be able to find cheaper/free alternatives.

Also, the website is completely absent of any indication of possible risks, like loss of data.