I recently bought a A1312 emc 2390 imac. It had no os. Guy I bought from said it would get to the internet installer (alt, command, r) high sierra, but would error out trying to reach installer server. I duplicated and used mr macintosh's fix # 3. Got past server error and when the installation started, the first odd thing I noticed was time started @ 9 minutes and within a few seconds dropped to 5 minutes, and @ 3 minutes install froze. Added a usb hard drive and tried to install to it. Same result. Built a high sierra usb install stick and everything went well until the install started. 9 minutes for a few seconds and then 5 minutes and froze around 3 minutes. Attempted several times with same result. Do I have a hardware problem? Also checked time and was off a few hours, but date was same. I tried with a ventoy usb with several flavors of linux. The live distros look great, but freeze up after a few minutes. Has anyone ran across this? No artifacts on screen, no lagging mouse, or anything, just freezes after a few minutes.