I have always wondered why there was never a big market[1] for "cheap PCI/PCI-X/PCI-e card you can stick a boatload of your old/surplus/n-generation old simms/dimms on and use as swap/slow memory/ram disk/etc". It's rare you can populate a motherboard with a full address space full of 'new' memory, and you can teach kernels to prefer some memory to others because of speed[2], so it seems like a no-brainer.
I seem to remember the market for doing similar with flash got neutered over patent issues, but I can't recall the details. And flash cache did end up being a market, at least for bigger players. Maybe something similar happened here, or maybe it just hit a niche I cared about at the time?
[1] I know there were a handful of products in this space, but my impression is they never really took off. I could be wrong.
[2] Definitely can in NetBSD; I've done it for archs like VMEbus where it's common to have a small, fast on board memory and much slower, often larger memory out on the bus. I assume this sort of thing is enabled in Linux by the work to support NUMA, but I've never looked into it.
I seem to remember the market for doing similar with flash got neutered over patent issues, but I can't recall the details. And flash cache did end up being a market, at least for bigger players. Maybe something similar happened here, or maybe it just hit a niche I cared about at the time?
[1] I know there were a handful of products in this space, but my impression is they never really took off. I could be wrong. [2] Definitely can in NetBSD; I've done it for archs like VMEbus where it's common to have a small, fast on board memory and much slower, often larger memory out on the bus. I assume this sort of thing is enabled in Linux by the work to support NUMA, but I've never looked into it.