> Why not just attach that RAM as system memory in such a situation? Because the number of available DIMM slots, and therefore total capacity, is scarce. Incre

> Why not just attach that RAM as system memory in such a situation? Because the number of available DIMM slots, and therefore total capacity, is scarce. Increases in capacity require increases in density, which carry a cost (and presumably power density and/or speed) premium. System memory scarcity is why swap is a thing in the first place. Having that extra RAM on a slower, farther bus, as swap, means it doesn't have quite as stringent performance requirements (or abilities) with the benefit of increased overall capacity. This tradeoff sounds familiar. > The point of using nonvolatile is that it's cheaper That has yet to be seen. It stands to reason that it'll be cheaper than the RAM that would otherwise go in the same DIMM slot, but it won't perform as well, either. We can be confident it will perform much better than even PCIe/NVMe SSDs. Is it cheaper than a generation or two ago's RAM in a big array (which, again, I know doesn't actually exist)? The main question is, given Intel's monopoly, what the real world price per performance is going to be like. > consumes less energy I hadn't really thought about this as a significant consideration, although at very large memory capacities a few watts here and there do add up, and it's certainly important when comparing anything new against anything old. Still, it seems like it would just be another cost factor.