I purchased a Mac Pro 1.1 in June 2014 in the hope of upgrading it a bit and making it my graphic design workhorse. It came with 2x3GHz dual core processors, 1GB ram, and an ATI 1900xt GPU. I purchased 16GB or ram to upgrade it the same time it came in. After upgrading the ram I upgraded Snow Leopard up to Mountain Lion, then ran the Tiamo boot efi for Mavericks. (Mavericks is enough for what I am doing I haven't messed with getting it to run Yosemite yet, but may want to if I can get past my problems). Well my Mac Pro had no real issues and it started running Mavericks just fine. Granted my GPU of 512MB was being read as 7-8MB or something minimal by the computer, but it was still working. I was using Chrome for browsing as it would flicker and look horrible trying to run Safari, but it managed to keep up okay with Adobe Illustrator, and would give a warning about not enough GPU when I started up Photoshop, but still seemed to work ok. So I used this setup up until the last month or so, but in the last month it seems like it just doesn't work, or doesn't send signals to my monitor, so even after starting up it would just leave a blank screen I have tried unplugging and what not but after probably 100 tries or so in two weeks I gave up out of frustration. Also to note is sometimes it would sound like a normal boot startup with the chime and all, other times it would kick on the fans really loudly, or make a strange slow whirring sound before the normal startup sounds, but regardless it would not work, nothing was showing up on my screen, making it worthless to me. So thinking it was an issue related to my GPU, as I have read a lot about that online, I purchased a flashed Radeon Sapphire 1GB 5770 GPU card, the authentic Apple ones were nearly twice the cost, so I figured save some $ and get the flashed version. I swapped out the 1900xt graphics card for this 5770, hooked everything in and started it up... How excited I was to see it working off of my first boot attempt. Overall the desktop screen looked much cleaner/better right off the bat. I checked my system stats, confirming it was reading 1024MB of video processing power. Safari worked like a charm, Photoshop opened without the usual warning I had been getting, watched some videos online and them seemed to run much better, everything seemed to be working well and I was very excited. I think I ran it maybe one more time the next day it worked fine, but the next time I tried to boot it up I was back to my same old issue again where it made the usual boot and chime sounds but then would not show anything on the screen at all, even after waiting a few minutes to boot, monitor was still not receiving a signal. I have been trying over and over, but to no avail, still getting the boot sounds, but nothing shows on the screen. I am not very tech or computer savvy and I have no idea what to do, this computer is worthless to me if I can't see anything on the monitor, and I really want to get it working again. Any ideas on helping me out with this problem would be appreciated. I might note that is occasionally doing some of the strange loud fan whirring and stuff at startup, but other times it just makes the normal startup sounds, just no video being sent to the monitor. This is driving me crazy not being as to just start and then use the computer. I was maybe wondering if I should get my usb that I used to put Mavericks on here originally and try that again, but feel like the screen still will not work making that nearly impossible to do. Any advice? Please help me!!!