Hi all. I have a 2009 4,1 -> 5,1 Mac Pro that has suddenly started to freeze randomly on me. Just after its 10th birthday, no less. This is driving me crazy because it is my main work machine which is normally running 24/7. Any help greatly appreciated. Symptoms, any of these can happen randomly but are guaranteed: No dong/chime/startup sound Freezes during startup Freezes during normal use (usually in <15 min. of boot) Sometimes after a freeze the machine will hard reset itself after some seconds, but only if it has fully booted SMC seems to still be active during freezes since holding the power button will eventually turn the machine off Relevant hardware specs: MacOS Mojave 10.14.4, so all the latest firmware updates and APFS support, etc. Dual x5680 CPUs that I delidded 64GB RAM (8GB x 8 1333MHz ECC Hynix Modules), all slots filled MSI Radeon RX 580 Gaming X 4GB Troubleshooting attempted: Swapped RX 580 for HD 5870 for boot screens, nothing unusual Pulled all drives and accessories Reseated all RAM modules and CPUs Tried running with 2/4/6 RAM modules Ran AHT, no problems found on quick test Wild guesses: Power Supply? Mainboard? I'm going to try to order a power supply and swap it out next week. But if that fails then I will likely have to dump the machine since I can't afford it to be down like this.