Use standard DIMM slots if available, otherwise consider UDIMMs for compatibility.
Use standard DIMM slots if available, otherwise consider UDIMMs for compatibility.
If you look at my signature, you see I have two Asus X79 systems doing UnRAID. You'll also see they're not really maxed out on RAM. Do have 8x8GB of DDR3 but it gives me problems, while all mostly of nearly the same type, some have slightly different PCBs and two of the sticks will not play nice with the other 6 and cause hangups, refuse to boot, crash, even at reduced clock speed. Any combination of the 8 sticks in in 4 stick kits works flawlessly, 6 of them also work fine in an 8 slot system, you add the two other to the other 6 and you have issues. Before anyone asks, no, this is an official X79 board, it does not support Registered/Buffered ECC, only Unregistered/Unbuffered ECC. (And I think the ECC function doesn't even work when using UDIMMs). I've tried it with RDIMMs. I've looked for BIOS mods. Nothing. RDIMMs will not work, only DIMMs or UDIMMs. So there is the queston, would it be cheaper to hunt down an 8x8GB DIMM or UDIMM kit? UDIMMs are not nearly as common on the used market as RDIMMs. ...Or as cheap, since the used market is flooded with RDIMMs.
Ignore ECC unless you're replacing X79 boards with real server boards using a C-series chipset. Intel removed ECC support from the X79, making RAM modules like UDIMM and RDIMM unnecessary. You'll be restricted to 8GB DIMMs without RDIMM compatibility, which unfortunately has no solution.
The discussion focused on which type of memory modules—RDIMMs or UDIMMs—is more affordable on the second-hand market, excluding the extremely low-cost RDIMMs.
Check the PC Part Picker for these choices; it can aid your search.
Visit their memory page for more details.