Pretty simple question. Is there any hardware for desktop PCs that allows you to add more DIMMs to the bus? I have seen this hardware for more expensive servers, but wondered if there was a similar setup that would be more cost efficient.
On a related question, if there is a limitation to the number of memory modules a computer can have, is it dependent on the CPU? I am thinking back to when I dealt with a dual Xeon processor workstation a while back and it had 3 DIMM banks for each CPU.
4 Answers
Short answer - no.
The reason that memory expansion boards you have seen in server systems were possible is that they used registered memory. There are no such boards for unbuffered memory. Also there is no need for it in desktop systems. Modern Intel desktop processors support up to 32 GB, many boards have 4 memory slots and 8 GB memory modules are readily available.
2I haven't heard of Memory expanders for desktop-class memory, and I haven't delved into server CPUs/architectures too much.
Desktop memory is usually capped by the CPU and/or the motherboard's northbridge, depending on the exact generation (Core i7 and later have the memory controller built into the CPU, for example, while earlier generations have it built into the motherboard's northbridge).
Some small form factor motherboards might not have the maximum slots due to size limitation, but if you browse the high-end ($200+) motherboards on Newegg for a given processor type, you should be able to pretty quickly find the maximum supported memory. Most desktop class CPUs currently available will max out at 2 slots per memory channel. You could in theory have a piece of hardware which joins two sticks of memory which are each half of a slot's maximum, but it would be slow, and not cost effective. The cost effective method would be to buy a motherboard which supports the maximum number of slots for that CPU.
2Short: No, you will not find any.
Long answer: Most memory controllers can only control a limited number of memory ranks per channel.
Usually 2 unbuffered (normal consumer) DIMMs per channel, or 3 buffered/registered DIMMS per channel. And since registered DIMMS buffer the output they are always slower by at least one cycle. As a result they only get used in servers where more bit slightly slower memory is preferred over less but faster memory.
If you need this memory capacity you will either: Get a motherboard, a CPU and a memory which is buffered. Or get a CPU and motherboard with more memory channels (e.g. i7 920 series with 3 memory channels and thus up to 3x2 DIMMS. Or find some rare (and expansive) low load DIMMs, get lucky and have a motherboard which supports that.
I'm rehabbing and old eMachine w3506. The owner of this Old Tower is poor and this was just sitting unused in the corner. I figured I'd try to help them out and get it running. Unfortunately I don't have any 1 gig ddr2 sticks lying around. This machine comes with two 512 sticks. The motherboard only supports up to 2 gigs of RAM and only has two slots. I have a bunch of 512 lying around. It would be great if there was a riser card that would allow one more slot on each side. So far I've managed to install an upgraded video card and Windows 10 64-bit. The motherboard supports SATA but is running on an 80gig IDE Drive. Of course an SSD and the two gigs of RAM would definitely show Improvement. Though the CPU is definitely a bottleneck. 720p YouTube videos are a bit choppy even with the Firepro V3800 pcie video card upgrade. Anyhow some memory Riser expansion Slot Cards would be great. The situation would probably be better off with a $50 octa-core, 2 gigabyte RAM, 16 ROM, Android TV box from eBay. Something like the s912...
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