So this is the good old Gigabyte GC Ramdisk PCI version.
It takes up to 1GB DDR1 sticks x4 to provide up to 4GB storage via SATA (1.0).
It was released when SSD tech was very new and expensive providing a fast effective and wear proof alternative.
Comes just as the card, I collected a few and will slowly sell half of those I have.
No ram or battery included (originals swell), eBay replacements available.
Some notes:
SATA1 interface limits bandwidth to 150 MB/s.
SATA1 interface was circa 2004-2007 after this SATA2 maintained good backward compatibility but SATA3 controllers are variable for working with older devices such as these GC-Ramdisks and depends on the chipset manufacturer.
My experience is that these GC-Ramdisks are incredibly fast for small files, faster than even modern nvme SSDs in 4K (Kilobyte) chunk performance and still limited by today’s CPU power for that metric. Max continuous bandwidth is of course limited by the SATA1 interface.
My favourite use for them is Windows 98, XP gaming and temp/scratch storage for raid volumes.