Comment by kjs3
2 days ago
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.
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.
That's a fair take and likely the answer.
I would counter tho that 1) this isn't the first time there's been a memory price/supply crunch, and "I've got a drawer full of last gen memory I can't use" is kinduva IT cliche, and 2) 'more memory' has always been a pain point, especially with industry practices like chipsets only supporting relatively small physical memory relative to address space (e.g. all those Intel LGA775 chipsets that capped at 4 or 8GB). Oh, and 2a) 'faster disk' has always been a pain point...
But, yeah...obviously my impression of things doesn't match market reality.
I think these products were always niche for the reasons parent suggested, I recall their price and max capacity being unappealing when I was looking to make use of a drawer full of obsolete RAM. But since there were several iterations from a few companies they must have sold well enough to justify their development.
They seemed to stop making them altogether around when SSDs came out which probably shrunk the market niche right out of viability.
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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.
That's not surprising. At the speed DDR4 runs, PCB design has to account for all sorts of weird effects. Adding the additional traces on the adapter probably pushes all sorts of timing over acceptable thresholds. There's a reason one of the big textbooks in the area is subtitled "A Handbook of Black Magic". [1]
[1] https://www.amazon.com/High-Speed-Digital-Design-Handbook/dp...
What board are you using that supports SODIMM? I’ve got 64GB I want to put in a workstation but I’m not finding the right solution.
30 years ago I remember cards like this to convert 4 30-pin SIMM modules to fit in a 72-pin SIMM slot.
https://www.ebay.com/itm/383521792853
I used to use 4 of those with that same branding, Simmverter, on my first Pentium system.
There were 4 variations of the ones I had, for each combination of Tall/Short and Forward/Backward. This way, 4 such adapters could be nestled together in a single set of 4 72-pin sockets without physical interference.
Each one accepted 4 30-pin SIMMs, for a total of 16 per 4-slot system.
It was not amusing trying to get all 16 SIMMs to work correctly at the same time, but it was inexpensive to get spares and I eventually got better at being deterministic about which module to swap out to attempt to improve reliability.
(Things got a lot better when sticks of 72-pin EDO became cheaper.)
Oh, yeah...I remember those. I prolly have one in a box someplace. They were pretty terrible. :-)
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.
You could give it a similar structure to CPU cache or a giant swap file. Have a giant blob of memory on the PCI RAM, that feeds the on board smaller motherboard RAM as needed. It might just work.
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.
However unless we're taking 3DXpoint which was discontinued flash wears out. But yeah sticking an old optane nvme on a breakout card accomplishes much the same thing.
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?
JBOD arrays are still a thing. They've even evolved a bit (see: UnRaid).
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.
Funny how the idea only seems to become practical once you have a literal warehouse problem worth of old RAM
Honestly DIMMs don't really fit on PCI cards and a boatload definitely doesn't fit.
They used to exist
Go back and read beyond the first sentence; you'll see I said exactly that.
Kind of. You referenced flash memory. However I owned an ibm ps/2 from the 80s which had an MCA memory card which could accept SIMMs and extend system ram. So maybe the previous poster is being pedantic? No need to downvote them
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