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I have updated/upgraded no less than 20, 2011 & 2012, Mac mini to 10.13.5 and all have been ok. All of them are using Apple OE (SK Hynix, Micron) RAM in a 2x8GB configuration and I have yet to have a single one fry a SO-DIMM or a RAM slot. Apple isn't purposely causing a RAM slot to stop working.

As of yesterday, I updated a 2012 Mac mini (MD387LL/A configuration) from 10.9.5 to 10.13.6 without a single issue related to the EFI update that occurred. It went from MM61.0105.B03 to MM61.010E.B00 so most of what is being mentioned in this thread has to be pure coincidence and/or hardware was failing and the OS update pushed it over the edge.
[doublepost=1542632844][/doublepost]Came apon tis thread after a loooon search. Hope it's still alive!
Midway through upgrading to MacOS Mojave from Sierra the Mini late 2012 started with the 3 chime issue. As was reported by others, only the top slot seem to accept an 8 GB RAM mod or the original 2 GB RAM mod after some testing. NVRAM/SMC resets had no effect. Can this be an EFI issue as wat reported by someone? Do I have to wait for a new OS release or may this be resolved by some OS update(s)?
thx

Les
 
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