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These are the modules I’m using, in the same configuration - the QVL lists a couple different variants of the MTA18ASF4G72AZ, just not the 3G2R, so I figured it was close enough.
So, they work - but I’ve not been able to get them running at the full 3200MHz. In fact, trying to change any memory related setting at all stops the system from booting, throws a C8 error on the debug LED, and according to the IPMI, causes the VCCM voltage to spike to 1.72V. Everything survives, but needs a BIOS reflash to get the system working again since it doesn’t even get to a point you can get into the BIOS, and the way the IPMI exposes it is… kind of terrible, honestly.
If you can get by without the full 3200MHz, it’s still worth getting them, since I’m sure someone smarter than me will figure out a way to get them running at full speed eventually, but I’ve had no issues running them at 2666MHz.
Interestingly, the BIOS does recognise them as being able to run at 3200MHz (and 2933MHz) when you go into the right menus, it just refuses to select it when set to Auto and throws those weird errors when you do it manually.