I think I had something similar, back in the DDR1 days. Mine was in a 5.25" format about the size of a CD-ROM. It was able to get closer to the SATA bandwidth

I think I had something similar, back in the DDR1 days. Mine was in a 5.25" format about the size of a CD-ROM. It was able to get closer to the SATA bandwidth max than anything I could afford with a RAID array of 10k drives. The IOPS were amazing, at the time. Had a battery backup and would cache to conventional disk. Was great for some DB operations.... with the understanding that it was not ECC ram and was a bit volitional. Main issue was the capacity. SSDs that came onto the market were a match for speed and PCIe drives crushed those I/O speeds again, without all the hassle.