I am working on a family member's Mac Pro 1,1 that they bought on eBay for cheap. It wasn't booting at all. I struggled to get the machine to see my patched El Capitan USB stick. However, after about a million random attempts, it booted to the USB when I held down the C key (why, I don't know but it worked). I installed the OS on the old HDD that came with the machine. It seems to work as expected. However, the family member now wants to upgrade to a 1TB Samsung SSD. The Mac Pro 1,1 recognized the drive but I can't boot to the USB again. Whenever I hold down Option on boot, the machine never loads. The flash drive's LED flickers repeatedly but the machine will never load anything. Adding to the problem is my lack of a boot screen. The machine as a GT120 installed but it must not be the version with the correct boot EFI files. I don't see anything on screen until it gets to the login screen. So, I have no idea what's happening when I hold down the Option key (or any key, for that matter). I've also tried selected the USB from the Control Panel "Start Up Disk" option but it doesn't appear as an option - only the El Capitan install on the old HDD appears as an option. Can you wonderful, kind, beautiful people recommend the steps I should take? I don't know if I should focus first on installing the OS to the SSD or if I should worry about the missing boot screens. Should I replaced the GPU? If so, I have NO idea what to get. The advice on the Internet is horribly confusing. Should I make a new install USB? TLDR: can't install El Capitan on my Mac Pro 1,1's new Samsung SSD. I suspect it's because I can't see any boot screens until the login prompt. How do I proceed?