RE: Just "installed" Radeon R7 250 graphics card on my Dell Optiplex 9020. Black screen when I plug the monitor into the card. Help!
TDP is not heat its power used. 75W and less cards get all of this power from the X16 Slot.
That means cards that use more than 75W have an Aux connector.
150W cards use 1 6 pin connector like the 750TI FTW in the previous post.
Cards that use more than 225W have an 8 pin and a 6 pin.
You cant spec a power supply by Watts and the 12v rails alone ignoring the 3.3v/5v rails or the +5VSP or -12v Rails.
Sappire support is very non helpful when you have CSM BIOS and need DOS VESA MODE 103 for F2 BIOS setup.
Earlier 5450 6450 6670 7750 7770 cards did not have this issue.