alt Hacker NewsI 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.
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Funny how the idea only seems to become practical once you have a literal warehouse problem worth of old RAM
Not exactly the same but I'm building a NAS box with old parts. Most of my spare RAM sticks are laptop DDR4 SODIMMs. There are SODIMM -> desktop DIMM adapters... it did not go well. The system would boot 1 out of 5 times. No adjustment of memory speed settings would make the system stable.
30 years ago I remember cards like this to convert 4 30-pin SIMM modules to fit in a 72-pin SIMM slot.
Old generation DIMMs are not that much cheaper and supply is limited as old generation are taken out of production to free capacity for newer chips. DDR2 is already more expensive than DDR3, likely because it is no longer produced but there is still demand (to replace/upgrade memory in older hardware).
My understanding (which could easily be wrong), is the big difference today is CXL which adds cache coherency on top of pci-e.
Without cache coherency, you have to be more careful about how you use the memory and the performance story is complex. Ram over CXL is going to have worse perf than ram on the cpu memory controller, but there shouldn't be any big gotchas.
Nvme drives already max out the 4x pcie lanes they get. You'd basically need to use the GPU slot to do better and even then you could do it with SSDs. M.2 break out cards are pretty common.
Cost for me. I wanted a Gigabyte I-ram but it was too expensive when I only had one 512MB DDR stick after upgrading to 4GB of DDR2. I bought a 60GB Sandforce SSD that fulfilled that speed gap.
Honestly DIMMs don't really fit on PCI cards and a boatload definitely doesn't fit.
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"
Reminds me of the days of JBOD arrays. Mac OS X had built-in support for it.
JBOR?
There was never a big market for it because new memory was not prohibitively expensive in comparison to the cost, risk, and limitations of using old memory in a new server. That is not the case now, so people are looking at the idea again.