Got hosed by a guy who said he was selling me a 2014 12-core 32gb Pro. It stopped running hours later, dead as a doorknob. Appears to be the motherboard. I get a quad core mid-2012 from a different guy, runs fine. When I put the 12-core 3.43 in, it runs fine, but the fans go full blast. I've zapped the PRAm reset the V. No joy. RAM is all good. Just can't get the fans off. It's running Mojave 10.14.4 no problems, but apparently needs a firmware update that the latest OS upgrade did not deliver. Only other weird thing is that it says my machine can only write APFS volumes. Gut-level is that I'll need to go to an earlier OS to get the firmware update, but I'm wide open to suggestions. I'm using this for DAW and Izotope plug-ins are VERY greedy. The quad can do it, but sometimes still red-lines even with 32gb of 1333 RAM. HELP!? Thanks, in advance, to any who are able to help.