This. Which is why Intel is working on Optane DIMMs.
Traversing the root complex can take upto 100 cpu cycles each way.
yep but Optane DIMM /NVDIMM is not for client product. It is on data center product list. Persistent Memory isn't just a concept on the textbook. It be realized now.
So was Optane at first and so were SSDs in general.
DDR4 already has an optional spec for NVDIMMs, DDR5 will make it mandatory.
Please forget Optane, just think about intel persistent memory. If you really care about performance /latency.