|A CPU is a large chip located under a heatsink/fan unit on your motherboard. You have no way of knowing whether or not your CPU is working if there is no display.|
You are on the right track testing your graphics and ram in another compatible system. Your next step is to test your problem system with the powersupply from your other working system. Disconnect all drive power & data cables and try booting up into BIOS setup.
If it boots up with a known good PSU then you have your answer. If it still won't boot up with a good PSU then it seems you have either or both of CPU or motherboard failure.
Goin' Fishin' (Some day)