No apple loading screen, not recognizing apple formatted hard drives.

I had just got this mac pro 5,1 from my father and it works but there's problems, the graphics card that came with it died, there's no boot screen (no signal for boot), and when i insert a mac os formatted hard drive it will not boot after letting it try to boot for 1 hour straight and many attempts.I have also tried a mac os snow leopard disc but no signs of a boot at all. I kinda think it can be the graphics card (AMD radeon hd 5670) but i dont know if i need to install drivers.When i installed mac os i did mac os x snow leopard and i made sure it would boot on a newer an older mac, but when i put it in my mac pro 5,1 (i might be wrong it may be 4,1) theres no signs of life. It does boot from window though.

System specs: dual 8 core intel xeon (stock) 16 cores total, 10 gigs ddr3 sdram, AMD Radeon HD 5670, 128 gig sandisk ssd, 1tb wd blue 5400 rpm drive. 2 optical drives.