A while ago, I upgraded the processor and RAM on my mid-2007 iMac so I could install macOS High Sierra. It now has an Intel Core 2 Duo Processor T9500 and 6 GB of RAM. Both the hardware and software upgrades went fine, but after using it for a while, I realized that the computer was much slower than before. Additionally, I didn’t like the iOS-inspired feel of High Sierra. Because of this, I decided to downgrade to Mac OS X Snow Leopard. I backed up my files, got my Snow Leopard Install DVD, and booted up the iMac. However, right after the language selection page, the installer read:
Mac OS X can’t be installed on this computer.
I opened disk utility and formatted the hard drive in case that was causing the issue, but I received the same error. I would have tried my Leopard install DVD, but it is an upgrade disk, not an install disk. So, I got out the factory restore disks to install Mac OS X Tiger. This installer ran successfully, and the computer worked fine after the installation. However, when I put in the Leopard upgrade DVD, I got the same error. Same with the Snow Leopard install DVD. I have tried every solution I could find; resetting the PRAM, formatting the hard drive, updating all my software, etc. Nothing works. The only thing I didn’t try was bypassing the hardware check in the installer for two reasons: (1) I don’t know if it will be the same for an Intel iMac as it is for a PowerPC Mac, and (2) It is incredibly difficult to get the required files on the iMac since Tiger doesn’t support TLS 1.2. I suspect that the issue was the CPU upgrade. Should I try this solution, or is there something else? If the bypass is the way to go, is there a simple way to download XAR from the iMac? I have been trying to get this to work for weeks and it’s been incredibly frustrating.