The products that used a PCIe X4 interface with a block storage protocol layered on top were never intended to deliver the best performance the memory was capable of.
Interesting - I wasn't aware, but even avoiding the PCI bus the performance must have been lacking as that link talks of "memory tiering". I guess this was "mid tier" somewhere between SSD and DRAM, which is a bit of a no-mans land especially in terms of conventional systems architecture ... really just a fast type of storage, or storage cache (a bit like a hybrid SSD-HDD drive).
