So I'm running into some issues with my Mac Pro 5,1 (2010). Backstory: Bought this thing used about a month ago. It ran fine, with the exception being the PSU would sometimes refuse to turn on the first time. Something known to happen on these machines after time. I threw in an SSD and a GT 1030, and used the machine just fine for about 3 weeks. Two days ago: I sold my main PC (timing right?) and got some money and a RX 570. I've been wanting to put a higher end AMD GPU for Final Cut in this machine. The 570 uses an 8-pin, I only have 2 6-pins, with a mini 6-pin to 8-pin coming the next day. I boot it up and wait. No chime, no video, nothing. The whole rig was getting power however. Fans spinning, LEDs flashing. I thought, hmm, maybe it's just not getting enough power. Pull it out, and put in a RX 280X I got earlier that morning, which uses a 8+6 pin for it's power. Same thing. So I pull that out, and put in the original GPU. Still same thing. This is when I start panicking. I try to reboot. Nothing. I tried putting it into EFI update mode by pressing and holding the power button while it's off. The power LED flashes, and the DVD drive ejects. Not knowing what it's for, I close it, and turn off the system. After doing some research, I came across the Firmware Restoration CD. I burn my first CD in years, and go through the process. the lights blink, but the DVD drive does not eject automatically. I pull it out and press the button manually. It opens. I pop it in, but nothing. I looked in the Service Manual. It tells me to pull out everything I can from the machine (processor tray, GPU, HDDs/SDDs, USB drives). Step by step, I put stuff back, pressing the DIAG button to display the diagnostic LED. 5V seems fine. Power seems ok. But when I put it back to a state where it could boot up, an "EFI DONE" LED should've come up a couple seconds after boot. It does, but then turns off. And then turns on again. And off. I'm really panicking right now because I just dropped a (relatively for a college student) large amount of money, and I have no computer for school. My old co-worker works at a Mac repair place, and he said something about the EFI chip being corrupted, and that this can reset it, which is something he has at work. While I don't doubt him, it's an 18 minute/$24 Uber ride there with a 50 lbs machine, and if it's something I can fix at home I would rather do that. Does anyone have any experience with these, and know what's going on?