Such things have existed for quite a long time...

For example:

https://en.wikipedia.org/wiki/I-RAM

(Not a unique thing, merely the first one I found).

And then there are the more exotic options, like the stuff that these folk used to make: https://en.wikipedia.org/wiki/Texas_Memory_Systems - iirc - Eve Online used the RamSan product line (apparently starting in 2005: https://www.eveonline.com/news/view/a-history-of-eve-databas... )

Are these the same thing though? I have a fondness for novel hardware and the idea of using up old ram standards to create a fast ram disk is interesting to me. But the CXL card seems to require motherboard/platform support whereas these older ram drives just showed up as a disk.