Mac Pro 1.1 Yosemite Crashing and reboot loop

[palmer007]

hi i have a mac pro 1.1 with 16gb ram, non efi asus 6670 pc graphics card with yosemite 10.10.5 on the ssd with pike's boot.efi,the mac will come on after the chime in about ten seconds , randomly freezes after using for 10+ minutes and i have to unplug the power cord.sometimes when i switch it on, it continuisly reboots every 3 seconds with the cpu a and b light flashing and the gpu fan speeding up and slowing down, i have tried every key when booting up,reset nvram-pram,smc and clean installs but cannot get this problem sorted,help would be much appreciated from anyone who has had this problem, thanks in advance