With Apple releasing an RAdeon update for its iMac models, it offered tools to be used for other purpose. Such tools have been improved an a dedicated utility has been developed: ATI Flashing tool.
In the ideal world, one can plug a PC RAdeon 4870 or 4890, next to the original graphic car, then turn it into a Mac Edition version. One can also use the software to install the application able to inject components required to recognize a non-flashed Radeon HD 4890, then reboot with this single card, flash it, then remove the injector and perform an ultimate reboot with a fully functional graphic carD.
You can download this software from the following URL: atiflashingtool1.0.zip
Warning: you need to have a graphic card strictly following the reference design released by ATI/AMD, and this is becoming increasingly difficult to find as most manufacturers try to increase RAM or GPU clock speed and amount to make their products "better".
