Answer to: Mac Pro 1,1 A1186 will boot and sleep, but not restart.The battery was going to be my next bet. For me, the exact same behaviour was a firmware issue as I had a Mac Pro 1,1 CTO and the firmware revision I had was somewhat special (higher version as the last released HW revision). I did a firmware upgrade to the Mac Pro 2,1 firmware and that solved the issue altogether. However, before doing that and getting rid of this problem, I changed the battery and it turned out that changing the battery momentarily solved the issue for 1-2 restarts, then the problem came back. I swapped cards, removed cards, tried out all kinds of things.... the FW upgrade solved it. Actually downgrading the firmware a step would have also solved it probably, but it was not possible. Update (05/07/2017): How are you unable to zap the PRAM? Power on, then immediately hold the alt-command-p-r keys... Oh, a thought. Plug your keyboard directly into the machine, don't go through a hub or a usb card!
Answer to: Why does my Mac Pro get stuck when I restart it?I got rid of the problem. My Mac Pro is restarting correctly 100% of the time now. Please, Sue, if you're reading. Confirm using System Profiler, that you have ROM version MP11.005D.B00 If so, I assume you have a CTO (customized-to-order) Mac Pro 1,1. Let me know.
Answer to: Why does my Mac Pro get stuck when I restart it?Actually the clicking noise the poster refers to (as I have the exact same problem) is the optical drive resetting... and since that power cycle goes in a loop, you hear that again and again and again along with the fans blowing and calming down, then blowing again, then calming down again... typical restart stuck at some point then starts over....